Add broker auto discovery (local)

[leonpegg]

add auto discovery to broker workers and clients as an option this will allow much faster deployment with less configuration. My recommendation would be to use http://rfc.zeromq.org/spec:20

[bmeck]

@leonpegg what about dns discovery, UDP broadcasts don't work on most public cloud infrastructure.

[leonpegg]

@bmeck DNS-SD is also an option

[prdn]

What about creating a repo pigato-discovery and use something like this https://github.com/agnat/node_mdns ?
I think it shouldn't be integrate in the main repo.
Then pigato-discovery could offer more discovery options such as udp.

[bmeck]

+1 to separate composable discovery module

[prdn]

This is nice https://github.com/wankdanker/node-discover