Clean up

A longer term issue, with some substeps, mostly for me (Reuben): - [x] Removing deprecated files: here, I'll defer to @JakobRobnik to identify files which no longer need to be in the repo - [x] Organization: all imgs+gifs should be in a single img dir, all notebooks (including tutorials) under notebooks, etc - [ ] helper function files in sampler/ should be in a utils subdir - [ ] all tests should be in tests/ - [x] some things like .egg files should be removed and/or gitignored