refactored test matrix to hopefully make Django matrix builds work on travis
Handle Django 1.3, which does not have a "IGNORABLE_404_URLS" setting by default
django.conf.urls.defaults has been deprecated in Django 1.4, not in 1.3
removed Django 1.2 from our build matrix
removed last traces of nose
remove Python2-inly dependencies from requirements-base.txt
pinned the versions of py.test related dependencies