Added virtual env to the tox.ini so the push to pypi will work correctly

Change-Id: I793a384cbba604c6c543c524c6c32217c590346a

tox.ini

@@ -3,13 +3,19 @@ envlist = py27,pypy,pep8
 skipsdist = True
 
 [testenv]
-commands = nosetests
+setenv = VIRTUAL_ENV={envdir}
+usedevelop = True
+install_command = pip install -U {opts} {packages}
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
+commands = nosetests
 
 [testenv:pep8]
 commands = flake8
 
+[testenv:venv]
+commands = {posargs}
+
 [tox:jenkins]
 downloadcache = ~/cache/pip