Rails 4 support

I love the package so far but the lack of proper Rails 4 support is saddening, so I put this little hack.

I don't use Python often, if ever, so it's a tad terrible, but it works absolutely fine. Best part is it keeps Rails 3 (and below) support.

Now, I tried to keep it DRY in `path_helper.py` by using the new `file_exists` function, but that seemed to break everything and the Sublime console wasn't very helpful with trying to fix it, but this currently works, and that's what matters.