use the latest Django version of the 1.3.x branch for security updates

See <https://www.djangoproject.com/weblog/2012/oct/17/security/> and
<https://www.djangoproject.com/weblog/2012/dec/10/security/> for details
on the fixed security issues.
Merge pull request #722 from cspurk/django-update

use the latest Django version of the 1.3.x series to get security updates