Add 2to3 in tox

tox.ini

@@ -9,6 +9,24 @@ deps =
      numpy
 
 # scipy cannot be installed by pip if numpy is not totally installed before
+[testenv:py26]
 commands =
     pip install scipy
     py.test [] --cov pygal pygal/test
+
+[testenv:py27]
+commands =
+    pip install scipy
+    py.test [] --cov pygal pygal/test
+
+[testenv:py32]
+commands =
+    pip install scipy
+    2to3 -w pygal
+    py.test [] --cov pygal pygal/test
+
+[testenv:py33]
+commands =
+    pip install scipy
+    2to3 -w pygal
+    py.test [] --cov pygal pygal/test