Add Travis testing for Django 2.0

Django 2.0 does not support Python 2.7, so it is not tested on that
combination.

We are now almost at 100 combinations on Travis...

Author: kevin-brown

.travis.yml

@@ -65,6 +65,8 @@ env:
     - TOX_ENV=py33-django1.11-drf3.6
     - TOX_ENV=py33-django1.11-drf3.7
     - TOX_ENV=py33-django1.11-drf3.8
+    - TOX_ENV=py33-django2.0-drf3.7
+    - TOX_ENV=py33-django2.0-drf3.8
     - TOX_ENV=py34-django1.6-drf2.4
     - TOX_ENV=py34-django1.6-drf3.0
     - TOX_ENV=py34-django1.6-drf3.1
@@ -95,6 +97,8 @@ env:
     - TOX_ENV=py34-django1.11-drf3.6
     - TOX_ENV=py34-django1.11-drf3.7
     - TOX_ENV=py34-django1.11-drf3.8
+    - TOX_ENV=py34-django2.0-drf3.7
+    - TOX_ENV=py34-django2.0-drf3.8
 
 
 matrix:

tox.ini

@@ -7,7 +7,7 @@ envlist =
        {py27,py33,py34}-django1.9-drf{3.3,3.4,3.5,3.6}
        {py27,py33,py34}-django1.10-drf{3.4,3.5,3.6,3.7,3.8}
        {py27,py33,py34}-django1.11-drf{3.5,3.6,3.7,3.8}
-       {py27,py33,py34}-django2.0-drf{3.7,3.8}
+       {py33,py34}-django2.0-drf{3.7,3.8}
 
 [testenv]
 commands = ./runtests.py --fast