def incoming(message, callback)
      if message['channel'] == '/meta/subscribe'
        authenticate_subscribe(message)
      elsif message['channel'] !~ %r{^/meta/}
        authenticate_publish(message)
      end
      callback.call(message)
    end
def incoming(message, callback)
      if message['channel'] == '/meta/subscribe'
        authenticate_subscribe(message)
      elsif message['channel'] !~ %r{^/meta/}
        authenticate_publish(message)
      end
      callback.call(message)
    end
Callback to handle incoming Faye messages. This authenticates both
 subscribe and publish calls.