Use version control tags to discover version numbers

 vcversioner autodiscovers a Python project's version number using
 version control system tags. This allows developers to avoid
 duplicating version information between their VCS and their setup.py
 metadata.
 .
 When the package is built, vcversioner generates a version.txt file
 that can be used for release tarballs.
 .
 Currently, vcversioner supports the git and mercurial (hg) VCS.
 .
 This module contains vcversioner for Python 2.x