Add link to terms and privacy policy to footer

https://trello.com/c/kvHopRjz
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.
* Memoize the HTTP requests.

[CoffeeLint]: http://www.coffeelint.org/
Remove unnecessary `if file.modified_line_at(line_number)`

* We operate only on diffs, so we know that the line number we have is one
  within the diff. The operation is unnecessary because the output we want is
  the line number, which is included in the input.