Add py34 to tox.ini

PyMongo has been tested against python 3.4 rc1 - rc3. We'll
probably wait until 3.4 final to update trove classifiers.

*NOTE* - Testing with 3.4 requires nose 1.3.1 due to
nose-devs/nose#759

Author: behackett

tox.ini

@@ -4,7 +4,7 @@
 # and then run "tox" from this directory.
 
 [tox]
-envlist = py26, py27, py32, py33, pypy
+envlist = py26, py27, py32, py33, py34, pypy
 
 [testenv]
 commands =