Add tox to test different python and django versions

.travis.yml

@@ -1,11 +1,40 @@
+sudo: false
 language: python
-python:
-  - "2.7"
-  - "3.4"
-  - "3.5"
-  - "3.6"
-script:
-  - flake8 django_migration_linter
-  - py.test
+
+matrix:
+    include:
+    - python: 2.7
+      env: TOXENV=py27-django19
+    - python: 2.7
+      env: TOXENV=py27-django110
+    - python: 2.7
+      env: TOXENV=py27-django111
+
+    - python: 3.4
+      env: TOXENV=py34-django19
+    - python: 3.4
+      env: TOXENV=py34-django110
+    - python: 3.4
+      env: TOXENV=py34-django111
+    - python: 3.4
+      env: TOXENV=py34-django20
+
+    - python: 3.5
+      env: TOXENV=py35-django19
+    - python: 3.5
+      env: TOXENV=py35-django110
+    - python: 3.5
+      env: TOXENV=py35-django111
+    - python: 3.5
+      env: TOXENV=py35-django20
+
+    - python: 3.6
+      env: TOXENV=py36-django111
+    - python: 3.6
+      env: TOXENV=py36-django20
+
 install:
-  - pip install -e ".[test]"
+  - pip install tox
+
+script:
+    - tox