Python3

This pull request makes the tests pass (and generally seems to make things work) under Python 3.3.

I tested with both `tcptests.py` and `sockettests.py` on Python 2.6, 2.7, and 3.3, with Django 1.4.5, 1.5.1, and 1.6a1. There are 2  tests (3 on `sockettests.py`) failing with "ResponseError: ERR Client sent AUTH, but no password is set" on all Python versions before and after the changes in this pull request.

I explicitly did not add support for Python 3.2, which does not support the "u" prefix on string literals. It would be possible to add this support, but I don't need it at the moment.