rtAudio Recompiled for OSX

Hey.
I was getting a lot of linker errors when using a ofSoundStream with this OSX lib presumable as it has not been re-compiled for cpp11. Here are the steps taken to fix:

* Cloned  openFrameworks-cpp11/apothecary 
* Ran $ ./apothecary update rtAudio
* Renamed `librtaudio.a` to `rtAudio.a`
* Replacing this new library with the one in openFrameworks-cpp11/openFrameworks.

Cheers.