Convert buildbot setup to Python 3
Add support for Python 3.x (especially 3.4.2+)
By default build with Python 2, not Python 3
Address @seancribbs's initial comments:
- actually return from __next()__
- use isinstance instead == to determine object type
- import print_function from __future__ for Python 2
- port assertItemsEqual() from Python2 to Python3
- actually run the YZ tests :astonished:
Make `six` a required package instead of an import in setup.py
Merge pull request #379 from basho/bch/feature/python3

Add Support for Python 3

Reviewed-by: seancribbs