TODO: Create automated tests

[KenBarr]

As per top level README:

1. Publish before initial connection. Async MQTT client calls connect then publish before connectComplete() is called.
2. Ensure message is stored as per persistent model then published once connection is established.
3. Cause reconnection. Once connected, disconnect the client at the message broker.
4. Ensure the client reconnects, validate subscription still exists for Clean=0 and do not exist for clean=1.
5. Publish while reconnecting. Connect client, publish at a rate of ~20/sec. Disconnect client at the broker.
6. Ensure reconnection and messages losslessly published in correct order.
7. Cause failover. Once connected, shut down access to connected MQTT router.
8. Ensure failover to next broker in host list. Subscriptions should re-add as per clean flag.