fixes #3: allow migrate to be run a second time


This allows running " ./manage.py migrate && ./manage.py migrate"  or "./manage.py syncdb && ./manage.py syncdb" to succeed on django 1.7.

I can't honestly say I've understood everything that the django 1.7 migrations are doing yet, but at some point it creates the database models using a module name of __fake__.

I think this is a safe change, but am not sure what the implications are for real-life migration scenarios.