Py3k

The patch includes the repo structure patch (for compatibilty with
other distros and the python compatibility patch.

Fixed cpopen.c to be a Python C extension compatible with the
versions above with a bit of ifdefing.

Fixed __init__ to expose a different _execute child due to python3's
exposing more positional arguments.

Fixed the tests to reflect that Popen now reads always in bytes
(while keeping python 2.6 compatibility).