Update tox matrix to match agreed support
Update tox matrix to match agreed support

See #1 for the discussion
glowka/django-admin-tools,miurahr/django-admin-tools,django-admin-tools/django-admin-tools,django-admin-tools/django-admin-tools,miurahr/django-admin-tools,django-admin-tools/django-admin-tools,eternalfame/django-admin-tools,eternalfame/django-admin-tools,glowka/django-admin-tools,miurahr/django-admin-tools,miurahr/django-admin-tools,glowka/django-admin-tools,eternalfame/django-admin-tools