Added Pipfile and Bootstrap Progress Bar

[byt3bl33d3r]

Hey!
First off insanely awesome project, I'm surprised this isn't more popular to be honest.

This commit adds a Pipfile to support installation using pipenv and a bootstrap progress bar (takes care of #48).

I'm not sure if this was the best way to implement it since I'm still getting familiar with the codebase, but hopefully it's a good starting point.

Cheers

[byt3bl33d3r]

Travis failed cause I used format string literals in the progressbar.py file. Let me know if you want me to change it to support python < 3.6.
Cheers

[tryexceptpass]

Hi thanks for the PR, I'd like to keep string literals, should probably change base support to 3.6+ ... It's just soooo much nicer. I promise I'll finish reviewing soon, very busy times both in and out of work these past few wks.

[tryexceptpass]

The only "required" package is autobahn, the rest are either dependencies, or packages required for the sample code:
*hypothesis is for testing, but i haven't written any tests with it yet, so we don't need it.

• asyncio is no longer needed since minimum python version is now 3.6.
• pytest is only required for testing.
• requests and tweepy are only required for the samples.