initial commit of configuration file for testing against Python3 (as well)

tox.ini

@@ -0,0 +1,12 @@
+# Tox (http://tox.testrun.org/) is a tool for running tests
+# in multiple virtualenvs. This configuration file will run the
+# test suite on all supported python versions. To use it, "pip install tox"
+# and then run "tox" from this directory.
+
+[tox]
+envlist = py27, py34
+
+[testenv]
+commands = {envpython} setup.py test
+deps =
+    networkx