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.