Moved from vanilla JS to React

[twolfson]

This PR transitions from vanilla JS to React. The application has full parity with its master counterpart (e.g. tray notifications, sidebar) as well as some new features. In this PR:

• Transitioned from vanilla JS to React
• Added documentation
• Added test for TeamStore
  • It might be difficult to test the application in full since we would have to mock over Slack
• Automatically updates sidebar upon login
• Started transition from iframe watcher for last active domain to using team_url from Slack
• Fixes Framework discussion #38

Notes:

This transition goes from 300 lines to 1000 lines but:

• It yields a known architecture
• 200 of those lines are new tests
• Handles DOM interactions automatically (e.g. no element tracking for addition/removal)

As mentioned in #38, there was a bit of friction with React's initial setup. Out of the box, there is no support for nw.js's HTML attributes like nwfaketop. As a result, we wrote an interim script to compile to get it to work. Before this PR lands, I will probably break that into its own repository.

/cc @wlaurance

[mathieumg]

🎉

[wlaurance]

👍 Looks great to me!

Should we wait for the interim script to be in its own repository?

[twolfson]

Nah, let's land it as is. That breakout can be done in a follow-up PR.

[twolfson]

@wlaurance It looks like you forgot to publish a release as this was landed =/ Going to release this as a minor release since everything should be at parity/backwards compatible