Tests leave effects!

[jdangerx]

I noticed when running tests that we don't actually reset the test database after our tests run! This is kind of funky, since it means the order of our tests matters - for example, by creating a table "test" in one set of tests, a different set of tests (that also wanted to create the table "test") would break. Depending on which tests run first, different ones would break. I can also go into mysql after running the test suite and see all the tables lying around.

I think that with Ecto/Phoenix there's some sort of Sandbox mode which lets us wrap the tests in a transaction that is then rolled back. Does it make sense to implement something similar for the Mariaex tests?