Pass on_delete to OneToOneField to handle Django warning
Pass on_delete to OneToOneField to handle Django warning

Fixes warning:

RemovedInDjango20Warning: on_delete will be a required arg for AutoOneToOneField in Django 2.0. Set it to models.CASCADE on models and in existing migrations if you want to maintain the current default behavior. See https://docs.djangoproject.com/en/1.10/ref/models/fields/#django.db.models.ForeignKey.on_delete

kabakchey/django-annoying,skorokithakis/django-annoying,skorokithakis/django-annoying,kabakchey/django-annoying