Create .gitkeep

Add `asset_held` to `account_history`.

Wait for pool.imap to finish before calling trader.train

Fix a slurry of bugs..

Fix TF hanging issue in multiprocessing pools.

Fix rendering of multi-process test environment

Allow multi-proc env to be rendered.

Replace deco with standard multiprocessing pool

Allow multi-process test to complete.

Merge branch 'litch-master'