Enable custom user model support with Django 1.5+

Authors: https://bitbucket.org/romanalexander, https://bitbucket.org/fuhrysteve
URL: https://bitbucket.org/codekoala/django-tracking/pull-request/5/fixed-django-15-support-retains-backwards/
Make Compatible with Django 1.6

Update the GeoIP import statements
Author: https://github.com/pcraston
URL: https://github.com/pcraston/django-tracking/commit/1fe23403f9db8c1691b4d8dfb6350e0e2d61c415