Fix setup.py, start work for py27 compat

While addressing Issue #1, realized that I've been using
3.4 for dev this whole time.  Minor tweak to kmeans.py,
and the setup.py changes so the script is found.

tox.ini revealed that my .so-finding function doesn't
work under tox - it's trying to load the .so from
the root of the project, not the .tox/* root.