Add testing for Python 3.6

.travis.yml

 language: python
-python: "3.5"
+python: "3.6"
 sudo: false
 cache: pip
 env:
   - TOXENV=py27-django111
   - TOXENV=py34-django111
   - TOXENV=py35-django111
+  - TOXENV=py36-django111
   - TOXENV=py34-django20
   - TOXENV=py35-django20
+  - TOXENV=py36-django20
   - TOXENV=py35-django21
+  - TOXENV=py36-django21
   - TOXENV=docs
   - TOXENV=lint
+matrix:
+  include:
+    - python: "3.5"
+      env: TOXENV=py35-django111
+    - python: "3.5"
+      env: TOXENV=py35-django20
+    - python: "3.5"
+      env: TOXENV=py35-django21
+  exclude:
+    - python: "3.6"
+      env: TOXENV=py35-django111
+    - python: "3.6"
+      env: TOXENV=py35-django20
+    - python: "3.6"
+      env: TOXENV=py35-django21
 install:
   - pip install tox
 script:

tox.ini

@@ -3,6 +3,7 @@ envlist =
     py27-django111,
     py34-django{111,20},
     py35-django{111,20,21},
+    py36-django{111,20,21},
     docs, lint
 
 [testenv]
@@ -11,13 +12,14 @@ basepython =
     py27: python2.7
     py34: python3.4
     py35: python3.5
+    py36: python3.6
 deps =
     django111: Django>=1.11,<2.0
     django20: Django>=2.0,<2.1
     django21: Django>=2.1,<2.2
 
 [testenv:docs]
-basepython = python3.5
+basepython = python3.6
 changedir = docs
 deps =
 	Sphinx
@@ -26,7 +28,7 @@ commands =
 	sphinx-build -W -b html -d {envtmpdir}/doctrees . {envtmpdir}/html
 
 [testenv:lint]
-basepython = python3.5
+basepython = python3.6
 deps =
 	flake8
 commands =