support coffeescript

[AndersDJohnson]

I'd like this to support coffeescript Gruntfiles. Is that something that's already available, or there's any interest in?

[shama]

I'd take a PR for adding a prompt whether to generate a gruntfile in coffeescript. There might be a yeoman generator that already does this otherwise it might be better to send a PR to https://github.com/yeoman/generator-gruntfile instead. Thanks