tox.ini: Add py33 to envlist
tox.ini: For py25, set PIP_INSECURE = 1 to work around lack of SSL
tox.ini: Comment out jython lines as they cause problems with
jython2.7b1
README.rst: code -> code-block for syntax highlighting
README.rst: A bit of reformatting
README.rst: Note support for Python 3.3