Add Python 3.5 classifier and venv

Now that there is a passing gate job, we can claim support for
Python 3.5 in the classifier. This patch also adds the convenience
py35 venv.

Change-Id: I7d4cf183edc8549755993cd4e27a982c06d75fd7
Depends-On: Ia9ddcf66c13def98b4b7df3b76f9f3dff53c42ca

setup.cfg

@@ -16,6 +16,8 @@ classifier =
     Programming Language :: Python
     Programming Language :: Python :: 2
     Programming Language :: Python :: 2.7
+    Programming Language :: Python :: 3.4
+    Programming Language :: Python :: 3.5
     Topic :: Internet :: Name Service (DNS)
 
 [global]

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 minversion = 1.6
-envlist = py34,py27,flake8
+envlist = py35,py34,py27,flake8
 skipsdist = True
 
 [testenv]
@@ -31,6 +31,10 @@ passenv = http_proxy
 commands =
   ostestr --blacklist_file=tests-py3.txt
 
+[testenv:py35]
+commands =
+  ostestr --blacklist_file=tests-py3.txt
+
 [testenv:docs]
 commands = rm -rf doc/build
            sphinx-build -E -W -b html doc/source doc/build/html