Minor fixes to include changes from Django 1.5

1. Removing Gunicorn's Django integration as [recommended](https://docs.djangoproject.com/en/dev/howto/deployment/wsgi/gunicorn/) in Django docs:

    > If you are using Django 1.4 or newer, it’s highly recommended to simply run your application with the WSGI interface using the `gunicorn` command as described above.

2. Including `ALLOWED_HOSTS` in production settings.