Fully async using promises

[betamatt]

A larger discussion piece. I'm having problems with pods right now so can't actually
get the damned thing to run.

Crashed out immediately, unable to find PromiseKit:
dyld: Library not loaded: @rpath/PromiseKit.framework/Versions/A/PromiseKit

[jonklein]

Yeah, that's the issue I was talking about with dynamic linking -- we'll need to restructure the project as a standalone app bundle rather than a command-line app to get this to work, which of course would have implications for actual deployability... not that that's a thing...

[jonklein]

I've done the restructure to the project to build Snell as a framework and should let us use Cocoapods (and requires that the demo be build as a .app) -- might be a painful merge, but should let this at least run.