Fix manage.py script for migrations.

manage.py

@@ -1,10 +1,13 @@
 #!/usr/bin/env python
 from flask.ext.script import Manager
-from flask.ext.migrate import MigrateCommand
+from flask.ext.migrate import Migrate, MigrateCommand
 
-from accountant import app
+from accountant import app, db
 
 manager = Manager(app)
+
+migrate = Migrate(app, db)
+
 manager.add_command('db', MigrateCommand)
 
 if __name__ == "__main__":