Adobe Generator/Slicy Support

Now that Photoshop has [Generator built
in](http://blogs.adobe.com/photoshopdotcom/2013/09/introducing-adobe-gen
erator-for-photoshop-cc.html) and tools like
[Slicy](http://macrabbit.com/slicy/) exist for older versions of
Photoshop, I think there's merit to naming all of the layers with the
filename they should be exported as.