Support for python 3

I don't know if this is on the roadmap for this project, but it would be nice! Even without rewriting everything, it might be possible to easily support python 3 by adding a line to `setup.py` that `2to3` should be run as shown [here](http://stackoverflow.com/questions/14501502/is-there-a-way-to-run-2to3-with-pip-install).
