Revert "Prepare for release 6.2.4.2"

The current version of python-readline (6.2.4.1) already works fine
on Mavericks. The modified patch 002a of commit 297055c simply removes
some potentially misleading error messages due to missing shared
library support (we build readline as a static library), as suggested
by commit 44bfb8d33.

When this becomes a proper readline patch in future, a new release
of python-readline will be triggered.
Remove unnecessary package installation

Travis comes with py.test pre-installed. Since version 1.4 (released
in 2010) the py package does not contain py.test anyway.
Merge branch 'master' into travis-ci.macosx

Test the latest version of python-readline on Mac OS X.