Coffeescript 1.7 support

CoffeeScript 1.7 no longer registers its `require()` `.coffee` handler by default; it now requires explicit registration like Streamline.

So updated the Streamline registration to ensure `.coffee` is registered, if we're registering `._coffee`. Tested this with my own node-neo4j module, which has a `util.coffee` file. Didn't work before, now it does.

Also fixed what I think is a bug: if you run `_coffee` on a non-`._coffee` file, or e.g. on a directory whose index file happens to be `.coffee` or `.js`, it wouldn't work previously, but now it does.