Just what the world needs, another silly Rust re-write! But it was a good exercise in learning.
There's a lot of messy things, which is why this is 0.2.0-pre.1. Going to make some cleaning passes after landing this.
Refactors the generator do to a two-pass:
1. Get a grasp of all directories which have images, noting their
children and images
2. Do stuff with those directories
