Add more Python versions to travis.yml

.travis.yml

@@ -3,6 +3,10 @@ language: python
 python:
   - "2.6"
   - "2.7"
+  - "3.3"
+  - "3.4"
+  - "3.5"
+  - "3.6"
 
 install:
   - python setup.py install