Properly transition to ES6 JavaScript from CoffeeScript

[Gert-dev]

Using the decaffeinate project the initial code has been converted to JavaScript (see #375 or 293eb20). This is just the first step however, as there are other things to do:

• Implement suggestions shown on top of each file
• Set up ESLint
  • Fix "atom" not being recognized by ESLint
  • Investigate enabling additional rules
  • Fix open issues shown by ESLint
• Rewrite to use ES6 modules instead of require syntax

[twifty]

My fix for "atom" not being recognized is a /* global atom */ at the top of the file. I also tend to also specify global itself as a global /* global global atom */, that way I can do thing like global.setTimeout without ESLint complaining. Other items like console.log I do on a per-line basis so as not to leave forgotten debug/dev helpers in the code.