First byte parsing of the remaining length
Second and Third byte parsing of the remaining length.  This is using the algorithm from the spec site pseudocode
Fourth byte parsing of the remaining length.
Updated the app.js whilst doing some manual testing with a python MQTT client paho
Added a quick test scratchpad.  Used the scratchpad to figure out how to encode the protocol name
Moved to a higher level MessageParser now.  Still working on the protocol name as this requires reading a UTF encoded string with a ruleset defined by MQTT