setup.cfg depends on the README file for its long description, so if
it's not in the source tarball, the build will bomb out. README.rst is an
automatically grokked name of a file for python and gets included
automatically. While we're dealing with this, add a MANIFEST.in to
ensure that AUTHORS and ChangeLog get installed too.
Change-Id: Id59fa5a6fecc179a80710ba8a5dc898fb713b1cf