Issue #57: First-pass at regression tests

Wow, that was more of a mission than I expected.

I suspect this isn't going to be enough or as complete as you were hoping for Mark. I might need to sit with Russell and just see what else I can/should be testing.

I decided to stick this in `ivory-cli` as it feels like we can/should add tests that aren't _specifically_ regression tests.

Before we merge I/we will need to release a "special" version for V0 (see `regression/v0` branch). I'll need to merge the `Hdfs.mv()` changes first.

/cc @markhibberd @raronson