Drop Python 3.3, add 3.6

.travis.yml

@@ -2,21 +2,23 @@ language: python
 
 python: 3.5
 
-env:
-  - TOXENV=py27
-  - TOXENV=py33
-  - TOXENV=py34
-  - TOXENV=py35
+matrix:
+  include:
+    - python: 2.7
+      env: TOXENV=py27
+    - python: 3.4
+      env: TOXENV=py34
+    - python: 3.5
+      env: TOXENV=py35
+    - python: 3.6
+      env: TOXENV=py36
+    - script: bin/check_for_differences
+      env:
+        - SUITE=Source
 
 install: pip install tox
 
 script: tox
 
-matrix:
-  include:
-    - script: bin/check_for_differences
-      env:
-        - SUITE=Source
-
 notifications:
   email: false

tox.ini

@@ -1,12 +1,12 @@
 [tox]
-envlist = py{27,33,34,35}
+envlist = py{27,34,35,36}
 
 [testenv]
 basepython =
     py27: python2.7
-    py33: python3.3
     py34: python3.4
     py35: python3.5
+    py36: python3.6
 deps =
     check-manifest
     readme_renderer