Ability to naviguate to current js/css file

Hello,

Don't pull this yet, it's not ready.

Two things:

* Make `projectile-rails-current-resource-name` be js/coffee/css/scss aware. This was easy (please check the regex)
* Write a `projectile-rails-find-current-javascript`, this didn't work. My guess is that `projectile-rails-find-current-resource` doesn't like to be given choice about file extensions... am I correct? how do you think we should tackle this?