diff --git a/Gemfile b/Gemfile
index a6b8823..60a20a7 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,33 +1,30 @@
 source 'https://rubygems.org'
-ruby "2.2.0"
-
-gem 'rails', '4.2.0'
-gem 'pg'
-gem 'sass-rails', '~> 5.0'
-gem 'uglifier', '>= 1.3.0'
-gem 'coffee-rails', '~> 4.1.0'
 
+gem 'coffee-rails'
+gem 'jbuilder'
 gem 'jquery-rails'
+gem 'pg'
+gem 'rack-cors'
+gem 'rails'
+gem 'sass-rails'
+gem 'sidekiq'
 gem 'turbolinks'
-gem 'jbuilder', '~> 2.0'
-gem 'sdoc', '~> 0.4.0', group: :doc
-
-gem 'rack-cors', '~> 0.3', '>= 0.3.1'
+gem 'uglifier'
+gem 'virtus'
 
-gem 'sidekiq', '~> 3.3', '>= 3.3.1'
-gem 'sinatra', '~> 1.4', '>= 1.4.5', :require => nil
+gem 'sdoc', group: :doc
 
-gem 'virtus', '~> 1.0', '>= 1.0.4'
+gem 'sinatra', :require => nil
 
 group :development, :test do
   gem 'byebug'
-  gem 'web-console', '~> 2.0'
+  gem 'foreman'
+  gem 'rspec-rails'
   gem 'spring'
-  gem 'rspec-rails', '~> 3.0', '>= 3.1.0'
-  gem 'foreman', '~> 0.77'
+  gem 'web-console'
 end
 
 group :production do
-  gem 'puma', '~> 2.11'
+  gem 'puma', '~> 3.12.1'
   gem 'rails_12factor', '~> 0.0', '>= 0.0.3'
 end
diff --git a/Gemfile.lock b/Gemfile.lock
index 2aff2e8..bab7b47 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,237 +1,245 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    actionmailer (4.2.0)
-      actionpack (= 4.2.0)
-      actionview (= 4.2.0)
-      activejob (= 4.2.0)
+    actioncable (5.2.3)
+      actionpack (= 5.2.3)
+      nio4r (~> 2.0)
+      websocket-driver (>= 0.6.1)
+    actionmailer (5.2.3)
+      actionpack (= 5.2.3)
+      actionview (= 5.2.3)
+      activejob (= 5.2.3)
       mail (~> 2.5, >= 2.5.4)
-      rails-dom-testing (~> 1.0, >= 1.0.5)
-    actionpack (4.2.0)
-      actionview (= 4.2.0)
-      activesupport (= 4.2.0)
-      rack (~> 1.6.0)
-      rack-test (~> 0.6.2)
-      rails-dom-testing (~> 1.0, >= 1.0.5)
-      rails-html-sanitizer (~> 1.0, >= 1.0.1)
-    actionview (4.2.0)
-      activesupport (= 4.2.0)
+      rails-dom-testing (~> 2.0)
+    actionpack (5.2.3)
+      actionview (= 5.2.3)
+      activesupport (= 5.2.3)
+      rack (~> 2.0)
+      rack-test (>= 0.6.3)
+      rails-dom-testing (~> 2.0)
+      rails-html-sanitizer (~> 1.0, >= 1.0.2)
+    actionview (5.2.3)
+      activesupport (= 5.2.3)
       builder (~> 3.1)
-      erubis (~> 2.7.0)
-      rails-dom-testing (~> 1.0, >= 1.0.5)
-      rails-html-sanitizer (~> 1.0, >= 1.0.1)
-    activejob (4.2.0)
-      activesupport (= 4.2.0)
-      globalid (>= 0.3.0)
-    activemodel (4.2.0)
-      activesupport (= 4.2.0)
-      builder (~> 3.1)
-    activerecord (4.2.0)
-      activemodel (= 4.2.0)
-      activesupport (= 4.2.0)
-      arel (~> 6.0)
-    activesupport (4.2.0)
-      i18n (~> 0.7)
-      json (~> 1.7, >= 1.7.7)
+      erubi (~> 1.4)
+      rails-dom-testing (~> 2.0)
+      rails-html-sanitizer (~> 1.0, >= 1.0.3)
+    activejob (5.2.3)
+      activesupport (= 5.2.3)
+      globalid (>= 0.3.6)
+    activemodel (5.2.3)
+      activesupport (= 5.2.3)
+    activerecord (5.2.3)
+      activemodel (= 5.2.3)
+      activesupport (= 5.2.3)
+      arel (>= 9.0)
+    activestorage (5.2.3)
+      actionpack (= 5.2.3)
+      activerecord (= 5.2.3)
+      marcel (~> 0.3.1)
+    activesupport (5.2.3)
+      concurrent-ruby (~> 1.0, >= 1.0.2)
+      i18n (>= 0.7, < 2)
       minitest (~> 5.1)
-      thread_safe (~> 0.3, >= 0.3.4)
       tzinfo (~> 1.1)
-    arel (6.0.0)
+    arel (9.0.0)
     axiom-types (0.1.1)
       descendants_tracker (~> 0.0.4)
       ice_nine (~> 0.11.0)
       thread_safe (~> 0.3, >= 0.3.1)
-    binding_of_caller (0.7.2)
-      debug_inspector (>= 0.0.1)
-    builder (3.2.2)
-    byebug (3.5.1)
-      columnize (~> 0.8)
-      debugger-linecache (~> 1.2)
-      slop (~> 3.6)
-    celluloid (0.16.0)
-      timers (~> 4.0.0)
+    bindex (0.7.0)
+    builder (3.2.3)
+    byebug (11.0.1)
     coercible (1.0.0)
       descendants_tracker (~> 0.0.1)
-    coffee-rails (4.1.0)
+    coffee-rails (4.2.2)
       coffee-script (>= 2.2.0)
-      railties (>= 4.0.0, < 5.0)
-    coffee-script (2.3.0)
+      railties (>= 4.0.0)
+    coffee-script (2.4.1)
       coffee-script-source
       execjs
-    coffee-script-source (1.9.0)
-    columnize (0.9.0)
-    connection_pool (2.1.1)
-    debug_inspector (0.0.2)
-    debugger-linecache (1.2.0)
+    coffee-script-source (1.12.2)
+    concurrent-ruby (1.1.5)
+    connection_pool (2.2.2)
+    crass (1.0.4)
     descendants_tracker (0.0.4)
       thread_safe (~> 0.3, >= 0.3.1)
-    diff-lcs (1.2.5)
-    dotenv (1.0.2)
-    equalizer (0.0.9)
-    erubis (2.7.0)
-    execjs (2.3.0)
-    foreman (0.77.0)
-      dotenv (~> 1.0.2)
+    diff-lcs (1.3)
+    equalizer (0.0.11)
+    erubi (1.8.0)
+    execjs (2.7.0)
+    ffi (1.10.0)
+    foreman (0.85.0)
       thor (~> 0.19.1)
-    globalid (0.3.0)
-      activesupport (>= 4.1.0)
-    hike (1.2.3)
-    hitimes (1.2.2)
-    i18n (0.7.0)
-    ice_nine (0.11.1)
-    jbuilder (2.2.6)
-      activesupport (>= 3.0.0, < 5)
-      multi_json (~> 1.2)
-    jquery-rails (4.0.3)
-      rails-dom-testing (~> 1.0)
+    globalid (0.4.2)
+      activesupport (>= 4.2.0)
+    i18n (1.6.0)
+      concurrent-ruby (~> 1.0)
+    ice_nine (0.11.2)
+    jbuilder (2.8.0)
+      activesupport (>= 4.2.0)
+      multi_json (>= 1.2)
+    jquery-rails (4.3.3)
+      rails-dom-testing (>= 1, < 3)
       railties (>= 4.2.0)
       thor (>= 0.14, < 2.0)
-    json (1.8.2)
-    loofah (2.0.1)
+    loofah (2.2.3)
+      crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
-    mail (2.6.3)
-      mime-types (>= 1.16, < 3)
-    mime-types (2.4.3)
-    mini_portile (0.6.2)
-    minitest (5.5.1)
-    multi_json (1.10.1)
-    nokogiri (1.6.6.2)
-      mini_portile (~> 0.6.0)
-    pg (0.18.1)
-    puma (2.11.0)
-      rack (>= 1.1, < 2.0)
-    rack (1.6.0)
-    rack-cors (0.3.1)
-    rack-protection (1.5.3)
+    mail (2.7.1)
+      mini_mime (>= 0.1.1)
+    marcel (0.3.3)
+      mimemagic (~> 0.3.2)
+    method_source (0.9.2)
+    mimemagic (0.3.3)
+    mini_mime (1.0.1)
+    mini_portile2 (2.4.0)
+    minitest (5.11.3)
+    multi_json (1.13.1)
+    mustermann (1.0.3)
+    nio4r (2.3.1)
+    nokogiri (1.10.2)
+      mini_portile2 (~> 2.4.0)
+    pg (1.1.4)
+    puma (3.12.1)
+    rack (2.0.7)
+    rack-cors (1.0.3)
+    rack-protection (2.0.5)
       rack
-    rack-test (0.6.3)
-      rack (>= 1.0)
-    rails (4.2.0)
-      actionmailer (= 4.2.0)
-      actionpack (= 4.2.0)
-      actionview (= 4.2.0)
-      activejob (= 4.2.0)
-      activemodel (= 4.2.0)
-      activerecord (= 4.2.0)
-      activesupport (= 4.2.0)
-      bundler (>= 1.3.0, < 2.0)
-      railties (= 4.2.0)
-      sprockets-rails
-    rails-deprecated_sanitizer (1.0.3)
-      activesupport (>= 4.2.0.alpha)
-    rails-dom-testing (1.0.5)
-      activesupport (>= 4.2.0.beta, < 5.0)
-      nokogiri (~> 1.6.0)
-      rails-deprecated_sanitizer (>= 1.0.1)
-    rails-html-sanitizer (1.0.1)
-      loofah (~> 2.0)
+    rack-test (1.1.0)
+      rack (>= 1.0, < 3)
+    rails (5.2.3)
+      actioncable (= 5.2.3)
+      actionmailer (= 5.2.3)
+      actionpack (= 5.2.3)
+      actionview (= 5.2.3)
+      activejob (= 5.2.3)
+      activemodel (= 5.2.3)
+      activerecord (= 5.2.3)
+      activestorage (= 5.2.3)
+      activesupport (= 5.2.3)
+      bundler (>= 1.3.0)
+      railties (= 5.2.3)
+      sprockets-rails (>= 2.0.0)
+    rails-dom-testing (2.0.3)
+      activesupport (>= 4.2.0)
+      nokogiri (>= 1.6)
+    rails-html-sanitizer (1.0.4)
+      loofah (~> 2.2, >= 2.2.2)
     rails_12factor (0.0.3)
       rails_serve_static_assets
       rails_stdout_logging
-    rails_serve_static_assets (0.0.4)
-    rails_stdout_logging (0.0.3)
-    railties (4.2.0)
-      actionpack (= 4.2.0)
-      activesupport (= 4.2.0)
+    rails_serve_static_assets (0.0.5)
+    rails_stdout_logging (0.0.5)
+    railties (5.2.3)
+      actionpack (= 5.2.3)
+      activesupport (= 5.2.3)
+      method_source
       rake (>= 0.8.7)
-      thor (>= 0.18.1, < 2.0)
-    rake (10.4.2)
-    rdoc (4.2.0)
-      json (~> 1.4)
-    redis (3.2.0)
-    redis-namespace (1.5.1)
-      redis (~> 3.0, >= 3.0.4)
-    rspec-core (3.1.7)
-      rspec-support (~> 3.1.0)
-    rspec-expectations (3.1.2)
+      thor (>= 0.19.0, < 2.0)
+    rake (12.3.2)
+    rb-fsevent (0.10.3)
+    rb-inotify (0.10.0)
+      ffi (~> 1.0)
+    rdoc (6.1.1)
+    redis (4.1.0)
+    rspec-core (3.8.0)
+      rspec-support (~> 3.8.0)
+    rspec-expectations (3.8.2)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.8.0)
+    rspec-mocks (3.8.0)
       diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.1.0)
-    rspec-mocks (3.1.3)
-      rspec-support (~> 3.1.0)
-    rspec-rails (3.1.0)
+      rspec-support (~> 3.8.0)
+    rspec-rails (3.8.2)
       actionpack (>= 3.0)
       activesupport (>= 3.0)
       railties (>= 3.0)
-      rspec-core (~> 3.1.0)
-      rspec-expectations (~> 3.1.0)
-      rspec-mocks (~> 3.1.0)
-      rspec-support (~> 3.1.0)
-    rspec-support (3.1.2)
-    sass (3.4.11)
-    sass-rails (5.0.1)
-      railties (>= 4.0.0, < 5.0)
+      rspec-core (~> 3.8.0)
+      rspec-expectations (~> 3.8.0)
+      rspec-mocks (~> 3.8.0)
+      rspec-support (~> 3.8.0)
+    rspec-support (3.8.0)
+    sass (3.7.4)
+      sass-listen (~> 4.0.0)
+    sass-listen (4.0.0)
+      rb-fsevent (~> 0.9, >= 0.9.4)
+      rb-inotify (~> 0.9, >= 0.9.7)
+    sass-rails (5.0.7)
+      railties (>= 4.0.0, < 6)
       sass (~> 3.1)
       sprockets (>= 2.8, < 4.0)
       sprockets-rails (>= 2.0, < 4.0)
-      tilt (~> 1.1)
-    sdoc (0.4.1)
-      json (~> 1.7, >= 1.7.7)
-      rdoc (~> 4.0)
-    sidekiq (3.3.1)
-      celluloid (>= 0.16.0)
-      connection_pool (>= 2.1.1)
-      json
-      redis (>= 3.0.6)
-      redis-namespace (>= 1.3.1)
-    sinatra (1.4.5)
-      rack (~> 1.4)
-      rack-protection (~> 1.4)
-      tilt (~> 1.3, >= 1.3.4)
-    slop (3.6.0)
-    spring (1.2.0)
-    sprockets (2.12.3)
-      hike (~> 1.2)
-      multi_json (~> 1.0)
-      rack (~> 1.0)
-      tilt (~> 1.1, != 1.3.0)
-    sprockets-rails (2.2.4)
-      actionpack (>= 3.0)
-      activesupport (>= 3.0)
-      sprockets (>= 2.8, < 4.0)
-    thor (0.19.1)
-    thread_safe (0.3.4)
-    tilt (1.4.1)
-    timers (4.0.1)
-      hitimes
-    turbolinks (2.5.3)
-      coffee-rails
-    tzinfo (1.2.2)
+      tilt (>= 1.1, < 3)
+    sdoc (1.0.0)
+      rdoc (>= 5.0)
+    sidekiq (5.2.5)
+      connection_pool (~> 2.2, >= 2.2.2)
+      rack (>= 1.5.0)
+      rack-protection (>= 1.5.0)
+      redis (>= 3.3.5, < 5)
+    sinatra (2.0.5)
+      mustermann (~> 1.0)
+      rack (~> 2.0)
+      rack-protection (= 2.0.5)
+      tilt (~> 2.0)
+    spring (2.0.2)
+      activesupport (>= 4.2)
+    sprockets (3.7.2)
+      concurrent-ruby (~> 1.0)
+      rack (> 1, < 3)
+    sprockets-rails (3.2.1)
+      actionpack (>= 4.0)
+      activesupport (>= 4.0)
+      sprockets (>= 3.0.0)
+    thor (0.19.4)
+    thread_safe (0.3.6)
+    tilt (2.0.9)
+    turbolinks (5.2.0)
+      turbolinks-source (~> 5.2)
+    turbolinks-source (5.2.0)
+    tzinfo (1.2.5)
       thread_safe (~> 0.1)
-    uglifier (2.7.0)
-      execjs (>= 0.3.0)
-      json (>= 1.8.0)
-    virtus (1.0.4)
+    uglifier (4.1.20)
+      execjs (>= 0.3.0, < 3)
+    virtus (1.0.5)
       axiom-types (~> 0.1)
       coercible (~> 1.0)
       descendants_tracker (~> 0.0, >= 0.0.3)
       equalizer (~> 0.0, >= 0.0.9)
-    web-console (2.0.0)
-      activemodel (~> 4.0)
-      binding_of_caller (>= 0.7.2)
-      railties (~> 4.0)
-      sprockets-rails (>= 2.0, < 4.0)
+    web-console (3.7.0)
+      actionview (>= 5.0)
+      activemodel (>= 5.0)
+      bindex (>= 0.4.0)
+      railties (>= 5.0)
+    websocket-driver (0.7.0)
+      websocket-extensions (>= 0.1.0)
+    websocket-extensions (0.1.3)
 
 PLATFORMS
   ruby
 
 DEPENDENCIES
   byebug
-  coffee-rails (~> 4.1.0)
-  foreman (~> 0.77)
-  jbuilder (~> 2.0)
+  coffee-rails
+  foreman
+  jbuilder
   jquery-rails
   pg
-  puma (~> 2.11)
-  rack-cors (~> 0.3, >= 0.3.1)
-  rails (= 4.2.0)
+  puma (~> 3.12.1)
+  rack-cors
+  rails
   rails_12factor (~> 0.0, >= 0.0.3)
-  rspec-rails (~> 3.0, >= 3.1.0)
-  sass-rails (~> 5.0)
-  sdoc (~> 0.4.0)
-  sidekiq (~> 3.3, >= 3.3.1)
-  sinatra (~> 1.4, >= 1.4.5)
+  rspec-rails
+  sass-rails
+  sdoc
+  sidekiq
+  sinatra
   spring
   turbolinks
-  uglifier (>= 1.3.0)
-  virtus (~> 1.0, >= 1.0.4)
-  web-console (~> 2.0)
+  uglifier
+  virtus
+  web-console
+
+BUNDLED WITH
+   1.16.1
diff --git a/README.md b/README.md
index 274bc5c..58b8e38 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
-# tech404 inviter
+# tech256 Inviter
 
-The application behind the [tech404 automatic invitation system](http://tech404.io)
+The application behind the [tech256 automatic invitation system](http://tech256.com)
 
 ## Usage
 
@@ -25,7 +25,7 @@ Pointing your web browser at the /sidekiq endpoint will give you access to Sidek
 
 Configuration items are stored in environment variables.
 
-* SLACK_SUBDOMAIN: e.g., tech404 for tech404.slack.com
+* SLACK_SUBDOMAIN: e.g., tech256 for tech256.slack.com
 * SLACK_TOKEN: an API token for an administrator of the organization ([more details](#slack_token))
 * SIDEKIQ_USERNAME: username for the sidekiq administration area
 * SIDEKIQ_PASSWORD: password for the sidekiq administration area
@@ -57,4 +57,4 @@ _Do not logout of the session where the token was generated._ If the token becom
 
 ## Deployment
 
-Deployed on Heroku. Ask @alindeman for access. In production, we run a puma process in the same dyno as a sidekiq worker. It's a hack to keep it free.
+Deployed on Heroku. Ask @iamvery for access. In production, we run a puma process in the same dyno as a sidekiq worker. It's a hack to keep it free.
diff --git a/config/application.rb b/config/application.rb
index 1643d3d..b3ac974 100644
--- a/config/application.rb
+++ b/config/application.rb
@@ -23,7 +23,7 @@ class Application < Rails::Application
     # Do not swallow errors in after_commit/after_rollback callbacks.
     config.active_record.raise_in_transactional_callbacks = true
 
-    config.middleware.insert_before 0, "Rack::Cors" do
+    config.middleware.insert_before 0, Rack::Cors do
       allow do
         origins "tech256.com", "tech256.github.io", "localhost:4000"
         resource "/invitations",