use https?+unix schema for support unix sockets
use https?+unix schema for support unix sockets

related: https://github.com/visionmedia/superagent/pull/961
visionmedia/superagent,fredigato/superagent,fredigato/superagent,focusaurus/superagent,craigspaeth/superagent,focusaurus/superagent,visionmedia/superagent,visionmedia/superagent,craigspaeth/superagent