net: add lookup option to Socket.prototype.connect

Allows customization of the lookup function used when
Socket.prototype.connect is called using a hostname.

PR-URL: https://github.com/iojs/io.js/pull/1505


Reviewed-By: Chris Dickinson <christopher.s.dickinson@gmail.com>
Reviewed-By: Yosuke Furukawa <yosuke.furukawa@gmail.com>