Enable use inside a virtualenv

Hard-coding the path to the interpreter causes problems when running
inside a virtualenv - eg, if pyyaml is installed inside the virtualenv
but not in the system python, this will give an import error rather than
finding the virtualenv's version of pyyaml
Update .gitignore to ignore virtualenv cruft
Add basic requirements
Basic packageization.

Readme has been tweaked to reflect the fact that this is now a more
generic tool.
Further packageization
Add tox.ini and test-requirements.txt

This will enable testing on patches pushed up to stackforge

Right now the tests fail, which is a sadness.