add tox target for python 3.4

Ubuntu 14.04 has python 3.4 so add a 3.4 target. 
Note that this will fail unless
you have new enough virtualenv. Recommend you install the packaged
version of 1.11.4 and get rid of any pip installed ones.

Change-Id: Ib54dc49fca2463f1c5cd788b48d06bd85be52655
Merge "add tox target for python 3.4"