Update to aludel 0.3.
Remove unnecessary empty line.
Switch to CollectionMissingError.
Support PostgreSQL and MySQL and test this on Travis.
Text(), not Text.
Handle MySQL timestamps better.
Move _drop_tables() back up to where it should be.
Update requirements now that aludel 0.3 has been released.
Merge branch 'feature/issue-8-aludel-0-3' into develop