If this line
from setuptools import find_packages, setup
is run after
from distutils.extension import Extension

a wrong Extension class is used

- version has to be obtained from file when no git repo is available
  like in tar-ball distributed by pypi

- updates in readme text
- added release script

This restructuring allows for easier separation of modules into
separate repositories later. Also, now pip install with repo url can be
used.

The setup.py files have also been updated to correctly reference each
other. Module versions are not extracted from git state