Support coffeescript

I know you're not a huge fan of coffeescript, but I enjoy it. I've always wanted to dive into streams and I somehow landed onto nodeschool.io. I think it's just brilliant.

If you don't want this to support coffeescript, that is fine. Feel free to close this pull request - but I figured others might enjoy solving these with coffee. If you want me to add this addition into the other nodeschool programs, I'd be more than happy to fork and send pull requests for those as well.

Thanks for this awesome tool!