Update CONTRIBUTING.md
Update CONTRIBUTING.md

Some minor edits and corrections.
annegentle/developer.rackspace.com,ktbartholomew/developer.rackspace.com,sigmavirus24/developer.rackspace.com,ktbartholomew/developer.rackspace.com,rackerlabs/developer.rackspace.com,rackerlabs/developer.rackspace.com,sigmavirus24/developer.rackspace.com,ktbartholomew/developer.rackspace.com,sigmavirus24/developer.rackspace.com,rackerlabs/developer.rackspace.com,rackerlabs/developer.rackspace.com,rackerlabs/developer.rackspace.com,ktbartholomew/developer.rackspace.com,ktbartholomew/developer.rackspace.com,annegentle/developer.rackspace.com,annegentle/developer.rackspace.com,sigmavirus24/developer.rackspace.com,annegentle/developer.rackspace.com,annegentle/developer.rackspace.com,annegentle/developer.rackspace.com,sigmavirus24/developer.rackspace.com,rackerlabs/developer.rackspace.com,ktbartholomew/developer.rackspace.com,sigmavirus24/developer.rackspace.com