[WIP] Xcode 6 Beta 5 Compatibility

Note that I'm still having problems compiling for both iOS and OS X – the frameworks both compile fine, but the tests won't compile. 

OS X tests generate the error "'AnyObject' is not identical to 'NSObject'" on the following line:

```swift
expect(signal.asSignalOfLatestValue().current as NSObject?).to.equal("foobar")
```

While iOS targets don't even get that far. They complain about a missing Quick module, and spew some warnings about missing architectures. I suspect this is because the Quick iOS and OS X frameworks have the same name, so that might require changing Quick. I'll keep you up to date.