Tracing/monitoring

[briggySmalls]

The events leaading to #97 have revealed a need for some event monitoring. There is currently no too way to review historic MQTT events, or trace them to SQS events.

To retrospectively diagnose issues this should be introduced.

[briggySmalls]

I've turned on AWS logging but I wonder if there is something better that could be done

[briggySmalls]

For the time-being, tracing from MQTT to SQS could be done via the "timestamp" property. This wouldn't scale to many customers, but given I have...ahem...one. That's fine