Yosemite: Brew OS Updates

More Yosemite changes. Within two weeks or so, Xcode 6 should be made available on the App Store, at which point 10.9 will need to go from “5.1.1” to “6.0” but whilst Yosemite is in Beta *everyone* should be using the Xcode Beta builds according to Apple, so Yosemite should be on 6.1 for the foreseeable, even when Apple releases Xcode 6.0 to 10.9 & below. 6.1 is still using the same Clang version number at this point.

I presume the intention is that by the time Yosemite is released Xcode 6.1 will be released with it, otherwise the transition for us could get a little dicey.

Worth noting - The Xcode path is now ``` /Applications/Xcode-Beta.app ```, with no numbering system in place.