Initial import of my changes to make pybonjour both python 2 & 3 compatible.

pybonjour.py
- usage of __future__.unicode_literals
- added compatibility code
- unicode text is better handled by functions
  - strings are either viewed as bytes or unicode
    to do this we alias unicode to str for python 3
  - fixed TXTRecord to behave better with unicode input
- reformatted code to make pep8 happier