title: How can Xcode 7 Stack Views be backwards-compatible with iOS 8 and iOS 7?
body: <p>I watched the WWDC video #407 - "Implementing UI Designs in Interface Builder" that present the cool feature - "Stack Views", and I was wonder that it would be wonderful (if it is possible) to build apps that will run on iOS 7, and 8 and take advantage of the new flexible UI layout abilities that Apple has added to Xcode 7.</p>