Some tested features

[dribnet]

Hi @IshmaelBelghazi - I thought it might be useful to document some of the more useful updates in my fork that could be merged back in:

• A script that allows training any generic fuel dataset (2fa2727)
• CLI improvements exposing --num-epochs, --z-dim, and --splits (67f2c7d)
• Options for image_size 128x128 (68cc868, works good) and 256x256 (37aee2f, never converged)
• Added --oldmodel option for starting training from existing model (2c80444)

All of this is tested and working well for me. Feel free to steal anything you want, or let me know if you'd like me to prepare a merge request with anything you see that would be useful.