Provide Version fix when project is copied to foreign GIT repository

Implement fix for Version to not cause Exception when the project's
source code is copied to a foreign GIT repository.

The fix is to specify an optional project-name, passed to Version. If a
name is provided, the code obtaining version information from GIT first
tries to verify we are in the correct GIT repository. A simple heuristic
was implemented, which checks the output of 'git remote -v' for the name
of the project.
Factor _git_cmd out of Version
Version: Strengthen derived repo-name
Rename Version.name to Version.reponame
Merge pull request #61 from melver/master

Provide Version fix when project is copied to foreign Git repository
Made version.py optional and added support for moving the .py files outside of the param package.
Minor rewording
Added abbrev() method to get simplified string representation
Set documentation version string automatically from project
Added 1.2.1 release notes and updated declared version
Minor clarification
Added numbergen.__version__
Added numbergen to manifest
Only verify version when uploading to PyPI (fixes #62).
Deleted trailing whitespace
Implemented Hash for platform independent hashes (time_dependent=True)
Deleted trailing whitespace
Cleaned up docstrings and comments
Switched order to numerator, denominator for readability
Fixed error when pickling Hash object due to internal struct