Add Django 2.1 to the Tox environments list.
Add Django 2.1 to the Tox environments list.

lpakula/django-oscar-paypal,evonove/django-oscar-paypal,st8st8/django-oscar-paypal,lpakula/django-oscar-paypal,evonove/django-oscar-paypal,st8st8/django-oscar-paypal,lpakula/django-oscar-paypal,django-oscar/django-oscar-paypal,django-oscar/django-oscar-paypal,st8st8/django-oscar-paypal,django-oscar/django-oscar-paypal,evonove/django-oscar-paypal