Access server, and server.address after calling app.createServer

[ariporad]

This should be easy, but when calling app.listen app.createServer (an io can only be attached to one server), it would be nice if the returned server was also available (later on) as app.server (app.io already is). It would also be nice (as a convenience), to have app.address be an alias for server.address

Todo list:

• Calling app.listen app.createServer sets app.server
• Calling app.listen app.createServer sets 'app.address`
• Document