Refactor dependencies and build tools

[ezekg]

I'd like to drop the Ruby, Grunt and Bower dependencies and switch to an NPM + Browserify (or Babel, depending on if we use ES6 over CoffeeScript) stack, using npm scripts as a build tool. Dropping CoffeeScript for ES6 is up for discussion, but I'd prefer to keep it. ❤️

Browserify seems the easiest to configure to allow ES6 and CoffeeScript at the same time. Here's a configuration that I've used before:

browserify -g [ babelify --presets [ es2015 ] ] -t [ coffeeify ] --extension \".js.coffee\" --ignore-missing