Begin work on running tests against the database:

* Add Travis postgresql setup.
* Replace "db mocks" with a before hook that creates the same data
  through the HTTP API.
* Reset DB and re-create all fixtures for each test. We'll need
  something  better here.
* CAVEAT: no concept of a dev vs test database. Running tests will
  clear data from the currently configured database.


This is a work in progress and shouldn't be merged as is.