Fixes tox.ini typo

tox.ini

@@ -19,7 +19,7 @@ commands = pip install -U -r{toxinidir}/requirements/dev.txt
                 --cover-inclusive --cover-min-percentage=94 --cover-erase []
 
 basepython =
-    2.7,flake8,flakeplus,apicheck,linkcheck,configcheck python2.7
+    2.7,flake8,flakeplus,apicheck,linkcheck,configcheck: python2.7
     3.4: python3.4
     3.5: python3.5
     pypy: pypy