Use matrix in travis config

This is needed to support python versions beyond 3.4

Author: JordonPhillips

.travis.yml

@@ -1,11 +1,20 @@
 language: python
-env:
-  - TOXENV=py26
-  - TOXENV=py27
-  - TOXENV=py33
-  - TOXENV=py34
-  - TOXENV=py35
-  - TOXENV=py36
+
+matrix:
+    include:
+        - python: 2.6
+          env: TOXENV=py26
+        - python: 2.7
+          env: TOXENV=py27
+        - python: 3.3
+          env: TOXENV=py33
+        - python: 3.4
+          env: TOXENV=py34
+        - python: 3.5
+          env: TOXENV=py35
+        - python: 3.6
+          env: TOXENV=py36
+
 sudo: false
 install:
   - travis_retry pip install tox