added the floor property from CLFloor needed for geolocation

In iOS 8 Apple introduced some APIs for indoor geolocation.
See: https://developer.apple.com/library/ios/documentation/CoreLocation/Reference/CLFloor_class/

There is also a slide deck from WWDC 2014 talking about this in more detail.
It is a trivial change, but a useful one. 

The only down side is that finding a list of building that have been mapped by Apple is a difficult task.