Remove support for py33/py26

Python 3.3/Python 2.6 is not supported from Mitaka, as per Infra.
The following patch removes the support for the same.

Change-Id: Ie138cdd5019ce762f7dfc8af5b0fa93c2d62ebfd
Closes-Bug: #1526170

Author: reedip

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py26,py27,py33,py34,pep8
+envlist = py34,py27,pep8
 
 [testenv]
 setenv = VIRTUAL_ENV={envdir}