Add support for Python 3.2 and 3.3

There is now a branch of Supervisor that supports Python 2 and 3. It is planned to be the next major release version. These changes get the supervisor-serialrestart tests passing on Python 3. 

A final step would be to add 3.2 and 3.3 to your tox and travis configs.  I did not do that because there is not yet a release version of Supervisor that installs on Python 3. If you have the Python 3 branch of Supervisor installed in your environment, and you remove "supervisor" from requirements.txt, the tests will pass.