switch from NSStream getStreamsToHost to CFStreamCreatePairWithSocketToH...

For me, this fixes dorianj#52 and probably fixes the problems some people are having on dorianj#50. The idea is to let OS X do the DNS lookup on its own. Built and tested on Mavericks with Xcode 5.1.1. I haven't tested elsewhere. The APIs used are not new, so it should be fine.