Check CoffeeScript using CoffeeLint

At my company we have quite a lot of CoffeeScript code, and I would love for Hound to be able to check CoffeeScript code too, not just Ruby. The current implementation only checks four rules, however if more rules are added to CoffeeLint they should be fairly straight-forward to add to Hound. The implementation does support customization through a `coffeelint.json` file, though.

TODO:
- [x] Update `app/views/application/configuration.haml`?
I opted to add this fallback to the line below, see 91468e45bd8fc45bff1cd0f9fd1287de5de60401.