Fix Travis and tox envlist

Replace python 3.3 and 3.4 with 3.5 and 3.6.

Signed-off-by: Yves Bastide <yves@botify.com>

Author: ybastide

.travis.yml

@@ -10,6 +10,7 @@ notifications:
   email: false
 env:
   - TOXENV=py27
-  - TOXENV=py34
+  - TOXENV=py35
+  - TOXENV=py36
   - TOXENV=nightly
   - TOXENV=pypy

tox.ini

@@ -4,7 +4,7 @@
 # and then run "tox" from this directory.
 
 [tox]
-envlist = py27, py33, py34, nightly, pypy
+envlist = py27, py35, py36, nightly, pypy
 
 [testenv]
 commands = nosetests --logging-level=ERROR -a slow --with-coverage --cover-package=bigquery