Update beaker to 1.6.4.

This update allows us to remove the patch for CVE-2012-3458, because
it's included upstream.
Update py-CherryPy to 3.2.4.

Also replaced downloads.cherrypy.org with MASTER_SITE_PYPI, because it
isn't up to date.
remove reference to emacs21. Issue reported by Martin Natano on github.