Add py36 env

While running `tox` command in binoic env, we see the following
message,
ERROR: InterpreterNotFound: python3.5
It is because the default py3 version for binoic is py36.
This patch adds the env in OSC also maintaining consistency
with setup.cfg

Change-Id: I8e5cf72901cba34ad44f2b356609f85b3b0c431f

Author: rajathere

Diff for: tox.ini

@@ -1,6 +1,6 @@
 [tox]
 minversion = 2.3
-envlist = py35,py27,pep8
+envlist = py36,py35,py27,pep8
 skipdist = True
 
 [testenv]