[FLOC-1042] PostgreSQL Acceptance test

Fixes https://clusterhq.atlassian.net/browse/FLOC-1042

If this is suitable, I will add the new dependencies (currently just the latest https://pypi.python.org/pypi/psycopg2) to `setup.py`. Each dependency must also go in the internal documentation for packages used.

This uses `psycopg2` which requires, on OS X for example ``brew install postgresql``. Perhaps it would be better to use http://python.projects.pgfoundry.org, a pure Python implementation. If not, should this just document that you need to install PostgreSQL?.
Yeah, got lucky, it just happened to come up one of the times I was running the tests while inspecting the code. It hit the `connect_to_postgres` method and came up with `pg8000.ProgrammingError: ('FATAL', '57P03', 'the database system is starting up')`