Remove unnecessary tests from tox.ini

At this point in time, tox is really only being used to run the test
suite. Once other pieces come are added, the tests can be restored.
Use in-memory database for test suite

While it is probably better to use Postgres for the test suite since
that is what is being used for both production and development, for the
time being an in-memory SQLite database will suffice. In order to make
it work, though, the database tables need to be created and destroyed
before each test that uses a request context.

There is probably a better way to do this. I should figure out what that
is.