Updated openstack/openstack
Project: openstack/ceilometer  9936b3469c833e88d8e39de4919d51b6bb21ff0b

Update documentation for new transformer

This patch adds documentation for the new multi-meter arithmetic
transformer.

Change-Id: I8e6f6040ad9865ed5e57a2462a4d2eb5ad56e11c
Closes-Bug: #1346883