Merge pull request #1 from crittercism/update_cookbook

Update cookbook
changed so that loopback_users attribute, if not defined, does not write loopback users at all. If defined, should be an array, either empty (for none -- means guest is usable remotely again -- beware!) or an array of usernames.
Merge pull request #3 from crittercism/loopback_users_via_attribute

changed so that loopback_users attribute, if not defined, does not write...
Make tcp listeners optional
Merge branch 'master' of https://github.com/crittercism/rabbitmq into clean_slate