Face Parts

@itsthatguy this is a pretty big refactor and I ended up merging master in, as well. The end result is it allows us to specify custom face parts.

Notes:
* If we have an 'eyes2.png', that translates to "eyes2" in the URL. 
* If the face part isn't found on the filesystem, it just isn't added to the image (this gets a little confusing because our image files aren't named sequentially)
* All parameters are required
* There's currently no resizing option for this route, we need to figure out how we want that to look.

It's up on staging, go check it out.
Good call, I'll move it.