Workflow tests

[eugenevinitsky]

The process of:

1. Spinning up a cluster with our current AMI
2. Running a quick exp and syncing to some s3 folder
   Should also be tested. The AMI breaks quite often and it'd be good to know it's coming.

[cathywu]

+100

[cathywu]

One possible consideration: it might cost us $$ to run tests, if we are spinning up EC2 instances every time we run unittests.