Test against Python 3.4

If it works in Python 3.3, it should also work in Python 3.4.
Considering it is the latest stable release, gitdb should be tested
against it.

Author: kevin-brown

.travis.yml

@@ -3,6 +3,7 @@ python:
   - "2.6"
   - "2.7"
   - "3.3"
+  - "3.4"
   # - "pypy" - won't work as smmap doesn't work (see smmap/.travis.yml for details)
 
 script: nosetests