Python 3 compatibility changes

Change import statements to from .x import y

Change dict.iteritems() to dict.items()

Force values to list in cases of dict.values() or map(f, list) or
filter(f, list)

Change xrange to range and use list(range) when code expects indices.

All tests pass on Windows/Linux Python 3.3.2
Change travis build to Python 3.3
Remove ABCMeta from links.LinkFunction and families.Family
Python 3 compatibility changes

Change import statements to from .x import y

Change dict.iteritems() to dict.items()

Force values to list in cases of dict.values() or map(f, list) or
filter(f, list)

Change xrange to range and use list(range) when code expects indices.

All tests pass on Windows/Linux Python 3.3.2
Change travis build to Python 3.3
Remove ABCMeta from links.LinkFunction and families.Family
Fix test_distributions from upstream to pass with Python3
Python 2 and Python 3 Travis
Change test_stat back. Don't know why I changed it in the first place
Merge pull request #385 from chadheyne/master

Python 3 compatibility changes