Add important migration to Django 1.8
Add important migration to Django 1.8

This migration makes `Person.last_login` NULL-able.

vahtras/amy,wking/swc-amy,wking/swc-amy,shapiromatron/amy,wking/swc-amy,pbanaszkiewicz/amy,swcarpentry/amy,vahtras/amy,vahtras/amy,shapiromatron/amy,wking/swc-amy,shapiromatron/amy,swcarpentry/amy,pbanaszkiewicz/amy,swcarpentry/amy,pbanaszkiewicz/amy