Fix travis.

.travis.yml

@@ -1,12 +1,25 @@
 language: python
-python:
-  - '2.7'
-  - '3.4'
-  - '3.5'
-  - '3.6'
+
 install:
   - pip install tox coveralls
+matrix:
+  include:
+    - python: 2.7
+      env:
+          - ENV=docs
+    - python: 2.7
+      env:
+          - ENV=py27-django18,py27-django19,py27-django110,py27-django111
+    - python: 3.4
+      env:
+          - ENV=py34-django18,py34-django19,py34-django110,py34-django111,py34-django20
+    - python: 3.5
+      env:
+          - ENV=py35-django18,py35-django19,py35-django110,py35-django111,py35-django20
+    - python: 3.6
+      env:
+          - ENV=py36-django18,py36-django19,py36-django110,py36-django111,py36-django20
 script:
-  - tox
+  - tox -e $ENV
 after_success:
   - coveralls