This changes allows additional node options to be defined after
the ip:port portion. Format will be:
IP:PORT:key=value:key=value:...
First two node options supported are 'weight' and 'backup'.
Also fixes a minor bug where 'raise' was being called without
defining what type of exception to raise. This works ok to re-raise
an existing exception, but raising a new exception requires a type.
Change-Id: I9b9883d100983a242002c95378bdbb672937ed90