[#52] Test Python 3.x support

Should at least be compatible with Python 3.4 now.
Can't get Python 3.3 to work locally, but let's see with Travis.

.travis.yml

@@ -5,6 +5,8 @@ language: python
 python:
   - "2.6"
   - "2.7"
+  - "3.3"
+  - "3.4"
 
 install:
   - python setup.py install

tox.ini

 [tox]
-envlist = py26,py27
+envlist = py26,py27,py34
 [testenv]
 deps=pytest
     pytest-pep8
     responses
-commands=py.test -v --pep8 mwclient tests
\ No newline at end of file
+commands=py.test -v --pep8 mwclient tests