powerline-daemon + mavericks = <3

In OS X 10.9 two things happened:

First I was getting compiler warnings -- including string.h fixed that.

Second, the client was super slow. After some debugging I found that the client wasn't connecting to the daemon and was always exec()ing powerline. Using the second (non __APPLE__) connect call turned out to be the right way to go, at least for 10.9. To gate it appropriately I changed the directive to only use the second connect on 10.9 and newer.