Added conflict for Django older than 1.4.0

Centos/RHEL shipped with Django-1.3 originally, those unfortunate souls
that installed before the Django14 need to remove Django and install
Django14.

Done via:
  yum remove Django
  yum install Django14

Another option could be to insist on upgrading to python-django15. Which
might be intrusive for more users but make it easier to obsolete django
1.4 in the future. Done via Conflicts: Django < 1.5.0
Merge pull request #424 from opinkerfi/rhel6-djangoconflicts

Added conflict for Django older than 1.4.0