Travis: Stop testing on unsupported versions of Django
Travis: Stop testing on unsupported versions of Django

Django versions prior to 1.8 are no longer maintained and so insecure:
https://www.djangoproject.com/download/#supported-versions

Removing them leaves all Python 2.6 permutations excluded, so the
redundant entries have also been removed. (Django 1.7 was the last
version to support Python 2.6.)

joke2k/django-environ