Adjust Description to Telemetry

Official OpenStack Naming was changed from Metering to Telemetry.
See
http://git.openstack.org/cgit/openstack/governance/commit/?id=9564eecb9769cb0fd52ff216b3e3172a6a323e3b
Merge pull request #41 from dirkmueller/release/roxy/master

Just a string change => merging