Added "clean" option to Makefile.
Made setup.py and Sphinx conf.py Python 3 compatible.
Ontje Lünsdorf (@thecom) and I ported the jnius package and the tests to Python 3. The same codebase no runs on Python 2 and 3. We tested it with Python 2.7, 3.2 and 3.3 under Linux and OS X.