0.3.0

• PEP8 cleanup.
• fix unintended _valid_part to valid_part variable name change in
  pan.config.
• handle type=user-id register and unregister response messages.
  suggested and initial diff by btorresgil.
• fix serial number (target API argument) not set in type=commit;
  from btorresgil.
• fix debug print to stdout vs. stderr in pan.xapi.
• changes for PyPI upload in setup.py.