python 3 compatibility, etc.

In case anyone is thinking about citeproc-py, this seems like a useful
overview of how to manage compatibility with the new Python 3.

http://lucumr.pocoo.org/cogitations/2008/12/07/porting-to-python-3-dos-and-donts/

It seems the basic suggestion is just to make sure that your code can
be automatically converted to being 3-compliant (using the 2to3 tool),
and to avoid py.test.

Bruce