Transpile ES6 even without node, just using rubyracer
Proof of concept: Load controller via ES6 module in Discourse
ES6: `AvatarSelector` and `HeaderController` - also includes support for controllers with
camelcase via an error message.
ES6: Uses proper `normalize` method, includes support for namespaced
controllers.
ES6: Half a dozen more controllers converted
ES6: More controllers converted to ES6
ES6: A bunch more controllers
ES6: More controllers
Remove unused stuff.