define CI test of training and inference

[cwsmith]

@jimlo7760 @sridhs21 I'd like to add a basic test of training (and inference, if possible) that runs quickly, with limited memory usage, for CI testing. Do you have any ideas on how that could be supported?

A few ideas:

• The simplest, and least meaningful, test I can think of is to just run training on 10 frames for a few epochs. This would at least catch python syntax and logic bugs.
• Writing and restarting from a saved model (see luy/load and save model #10) then running a few epochs on limited frames.

[cwsmith]

closed with #14