add initial alembic files, point at tahrir.db, and basic readme
Add swap file extensions to .gitignore
Make Alembic run migrations as a transaction, rolling back on OperationError. Also add a migration script to add a column.
Print repr() of OperationalError.
Add 3 more Alembic scripts to complete Tahrir model changes for now.
Merge branch 'feature/alembic' into develop