Updated dependencies in tox.ini to latest supported versions of Django

tox.ini

@@ -16,23 +16,23 @@ deps =
 [testenv:py27-django14]
 basepython = python2.7
 deps =
-     Django==1.4.10
+     Django==1.4.15
      {[testenv]deps}
 
 [testenv:py27-django15]
 basepython = python2.7
 deps =
-     Django==1.5.5
+     Django==1.5.10
      {[testenv]deps}
 
 [testenv:py27-django16]
 basepython = python2.7
 deps =
-     Django==1.6.1
+     Django==1.6.7
      {[testenv]deps}
 
 [testenv:py33-django16]
 basepython = python3.3
 deps =
-     Django==1.6.1
+     Django==1.6.7
      {[testenv]deps}