Add a .gitignore
Drop use of 2to3

Rewrote the source to be compatible with all Python versions (with the
help of python-modernize, and, when that proved to be woefully
inadequate, 2to3).

Introduced a dependency on six, because I can't be bothered to figure
out how to implement six.reraise() on my own.
You can now use buildout on Python 3