[Fix bug 1275551] Enable django security middleware.
[Fix bug 1275551] Enable django security middleware.

Sets the following HTTP headers:
 - X-XSS-Protection: 1; mode=block
 - X-Content-Type-Options: nosniff

johngian/mozillians,mozilla/mozillians,akatsoulas/mozillians,akatsoulas/mozillians,fxa90id/mozillians,akatsoulas/mozillians,fxa90id/mozillians,johngian/mozillians,mozilla/mozillians,akatsoulas/mozillians,fxa90id/mozillians,mozilla/mozillians,mozilla/mozillians,fxa90id/mozillians,johngian/mozillians,johngian/mozillians