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: I87d6445a451e380a290f4a6cf9364c621dc293e5

setup.cfg

@@ -17,6 +17,7 @@ classifier =
     Programming Language :: Python :: 2.7
     Programming Language :: Python :: 3
     Programming Language :: Python :: 3.4
+    Programming Language :: Python :: 3.5
 
 [files]
 packages =

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 minversion = 1.6
-envlist = py34,py27,pep8,functional
+envlist = py35,py34,py27,pep8,functional
 skipsdist = True
 
 [testenv]
@@ -53,6 +53,10 @@ commands = oslo_debug_helper {posargs}
 basepython = python3.4
 commands = oslo_debug_helper {posargs}
 
+[testenv:debug-py35]
+basepython = python3.5
+commands = oslo_debug_helper {posargs}
+
 [testenv:pep8]
 commands =
     flake8 senlin