Add pre-publish-send-email hook example script

This example script file shows how a pre-publish-send-email hook can
validate a patch emails before they are sent.

Signed-off-by: Stefan Hajnoczi <stefanha@gmail.com>
Add Red Hat copyright to git-publish

I have been working for Red Hat since late 2012 and recent changes are
therefore copyright Red Hat.

Signed-off-by: Stefan Hajnoczi <stefanha@gmail.com>