generic message format which matches the HTTP API v2
    
    Fixes #92.
    
    This changes the message structure to contain the complete result data,
    in the same format as the HTTP API v2.
    
    Existing message structure and de-duplication logic is preserved in the
    new publish_taskotron_message() function, which is disabled by default
    but can be enabled for backwards compatibility by setting
    MESSAGE_BUS_PUBLISH_TASKOTRON=True. This function is hardcoded to only
    send on fedmsg and with 'taskotron' as the topic.