Using coffee-script for gulpfile will break with the next release of CS

Created by: xixixao

With the next release of CS, requiring coffee-script won't autoregister .coffee extensions. Instead, requiring coffee-script/register will be required.

This can be fixed by changing the README when the time comes, but I'd opt for a different solution, that would allow .coffee config without having to specify the registration every time (short of an alias).

See https://github.com/jashkenas/coffee-script/pull/3279