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).
Although this warning is important, perhaps it's current wording is a little too strong. The filter _might_ prevent an attack, but can not be relied on. Perhaps something like:

```
The browser XSS filter is a useful additional defense measure, but must not be relied on.
It can not detect all XSS attacks and not all browsers might support it.
Always ensure you are still validating and sanitizing all input to prevent XSS attacks.
```
(linking to https://docs.djangoproject.com/en/dev/topics/security/#cross-site-scripting-xss-protection)