WIP: Integrating django-secure

For background info, please see the [django-developers thread](https://groups.google.com/d/topic/django-developers/t8ybImtdnpM/discussion).
Minor wording nit; the "and" reads oddly to me here, I might replace it with a semicolon? And replace "change this" a couple lines down with "change it to 'DENY'", for clarity.