Use git.openstack.org instead of github.com since git.openstack.org is
the reference for OpenStack
Change-Id: Ife876952105f24383b4a03511018c04a4d4d655a
Overview
--------
-The ceilometer module is part of [OpenStack](https://github.com/openstack), an effort by the
+The ceilometer module is part of [OpenStack](https://git.openstack.org), an effort by the
OpenStack infrastructure team to provice continuous integration testing and code review for
OpenStack and OpenStack community projects as part of the core software. The module itself
is used to flexibly configure and manage the metering service for OpenStack.