update tox to django 2.0 beta1 (#5507)
update tox to django 2.0 beta1 (#5507)


kgeorgy/django-rest-framework,jpadilla/django-rest-framework,jpadilla/django-rest-framework,kgeorgy/django-rest-framework,dmwyatt/django-rest-framework,tomchristie/django-rest-framework,kgeorgy/django-rest-framework,tomchristie/django-rest-framework,dmwyatt/django-rest-framework,dmwyatt/django-rest-framework,jpadilla/django-rest-framework,tomchristie/django-rest-framework