Write an acceptance test suite

[sgraf812]

This is hard to test, but it sucks so much more not to have automated tests.

Planned acceptance tests:

• [x] --check: malformed and well-formed config files
• [x] --one-shot mode: single/multi repo, with/without deployment
• [x] daemon mode: reaction to config file changes, periodic refetch
• [x] parallelization: master-only and slave-only