All unit tests now pass under python 2.7 and 3.3.

- Ran 2to3 on entire module.
- Added "from __future__ import division, print_function, unicode_literals"
  to all files.
- Added utilties/python23.py for functions dealing with python 2/3 compatibility.
- Miscellaneous fixes for:
  - integer division (//)
  - unicode vs. byte arrays/strings
  - __builtin__ vs. builtins
  - etc.
Remove __future__ imports from setup.py.

Added python 3.3 and 3.4 to travis script.