Fixed #17101 -- Integrated django-secure and added check --deploy option

For background info, please see the [django-developers thread](https://groups.google.com/d/topic/django-developers/t8ybImtdnpM/discussion).
As it is recommended to "use a small value for testing `SECURE_HSTS_SECONDS`", I don't see a problem in `SECURE_HSTS_INCLUDE_SUBDOMAINS` defaulting to `True`. Alternatively, we could schedule this change in one or two releases.