Concurrency in Python

This is a maintenance release for Python 0.13.0, fixing a number of
issues. Read the changelog for details. Get it from PyPI.

Thanks to Ralf Schmitt who worked with me on this release.

Thanks to the following people who provided patches: David Hain, Teh
Ekik, Dmitry Chechik, Alexey Borzenkov, Antoine Pitrou, Örjan Persson.

Thanks to everyone who reported bugs and participated in the discussion.

Thanks to Leif K-Brooks (Omegle.com) and Spotify who
responded to the sponsorship call and provided funds for gevent
development!