Add beginnings of Kademlia gather module and protocol support
Add proper peer decoding
Mostly complete Kademlia PING / BOOTSTRAP scanner
Minor style/test cleanup
YARD and spec cleanup
Initial commit of more OO version of Rex/Aux Kademlia support
Partial commit
Move Kademlia stuff to a more OO model, etc, per reviews

All of the work is done in rex.  The msf mixin just prevents the
desire to call rex directly from the module
Doc cleanup
Add minor missing doc
Downcase the service name for consistency
Add Kademlia scanner, lands #4210