Use absolute import for 'django'

Avoids importing same file (teamcity/django.py) instead of the real
django. Only necessary for python 2.
Python3 workaround
Bugfix incorrect class in super call
Merge pull request #36 from denisenkom/python3bugfix

Bugfix incorrect class in super call
Merge pull request #34 from denisenkom/master

Python3 workaround
Merge pull request #32 from mfogel/absolute-django-import

Use absolute import for 'django'
Merge remote-tracking branch 'origin/master' into tests