tox: explicitly test with Python 3.2 an 3.3
tox: test with Python 3.4

No code change needed.
tox: add support for Python 2.6

The OrderedDict class was added to the stdlib in Python 2.7. There is
a drop-in replacement on PyPI, but this does not work for Python 3, so
we still try importing the stdlib collections module first.
README: document supported Python versions
setup: don't rely on setuptools

We actually don't need setuptools for anything substantial so we can
just use the stdlib distutils instead. This fixes a build error when
pip (and thus setuptools) isn't installed in a LXC container.
Merge pull request #33 from mgeisler/tox-more-python-vers

tox: test more python versions