Auth Changes For Statsd Backend

* This module now gets a token at the first flush from Cloud Identity if Rax Username and Api key are supplied.
It uses that token for all posts to the CM endpoint. 
* If it gets a 401 from the CM endpoint, it again queries Identity for a new token. It then replaces the x-auth-token header with the new token.
can you change all of the points that were modified to accept user name and API key to accept an object (called `authCredentials` or something like that)?

My thinking is that this will leave the APIs flexible enough to support other auth mechanisms that may not require api keys or user names.