Add CoffeeScript support

* Use [CoffeeLint] to keep to a community-supported open source standard.
* Propose a `.hound/ruby.yml` and `.hound/coffee.json` naming convention.
* `.hound.yml` will still work (backwards compatible) but would now be
  considered legacy / deprecated.

[CoffeeLint]: http://www.coffeelint.org/
It looks like I am actually wrong about that. We're using `Coffeelint.lint`, not `Coffeelint.lint_file`.

https://github.com/zmbush/coffeelint-ruby/blob/master/lib/coffeelint.rb#L42-L52

So, this should be able to be removed.