Quieter unit tests

I couldn't find any options while perusing the alembic documentation
that specifically controlled logging, plus control of everything seems
to fall under the env.py umbrella, so I decided I would leave logging
unconfigured unless it was otherwise necessary.

There are still a handful of warnings that appear in the test run that
can be cleaned up later, but at least the entire run fits on one screen
again.
Merge pull request #205 from Cerberus98/master

Quieter unit tests