Update copyright in license file to add HP 2013

Change-Id: I7883c19b3a18b6bc0cc23b228551b401b1ac93dc
Reviewed-on: https://review.openstack.org/21458
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: Anita Kuno <akuno@lavabit.com>
Approved: Dan Prince <dprince@redhat.com>
Reviewed-by: Dan Prince <dprince@redhat.com>
Tested-by: Jenkins