Add a SQL test

[raylu]

http://docs.sqlalchemy.org/en/latest/orm/session_transaction.html#joining-a-session-into-an-external-transaction-such-as-for-test-suites after the test runs:

$ psql -U statbot_test

statbot_test=> select * from users;
 user_id | name | discriminator | avatar | is_deleted | is_bot 
---------+------+---------------+--------+------------+--------
(0 rows)