postgres: Initial TemporaryDatabase implementation.
postgres: Add database cleanup.
postgres: Add environment variable exporting.
postgres: Add docs.
travis.yml: Disable container-based builds.

We need to start postgres & rabbitmq so we cannot disable sudo :(
travis.yml: Add rabbitmq service.

Removing this had no effect on our build failures so we might as well
enable it and test all code paths.
integration/test_postgres: Switch to travis supported options.

Travis-CI supports a limited number of locales in their postgres stack
and I chose an unsupported one when testing options support.  This
commit switches to one that is documented as supported.
travis.yml: Removing pypy support.

Psycopg2 is known to not support pypy.  If we want to test against pypy,
then we will have to work through this separately.
Merge pull request #11 from aweber/add-postgres

Add postgres helper