Test under tox: Python 2.6, 2.7, 3.3, 3.4.

python/tox.ini

@@ -0,0 +1,13 @@
+[tox]
+envlist =
+    py26,py27,py33,py34
+
+[testenv]
+usedevelop = true
+setenv =
+    LD_LIBRARY_PATH={toxinidir}/../src/.libs
+commands =
+    python setup.py -q --cpp_implementation develop
+    python setup.py -q test -q
+deps =
+    six