Update django_authgroupex_dev settings to Django 1.7

This silences this warning when running "python manage.py test":

    Django 1.6 introduced a new default test runner. It looks like
    this project was generated using Django 1.5 or earlier. You should
    ensure your tests are all running & behaving as expected. See
    https://docs.djangoproject.com/en/dev/releases/1.6/#new-test-runner
    for more information.

cf. https://github.com/django/django/blob/1.7/django/core/checks/compatibility/django_1_6_0.py#L17
Make Travis test development site too