Xcode 6 + ios8 SDK但在ios7上部署(UIWebKit & WKWebKit)

We are creating an app using Xcode 6 beta 5 + Swift on iOS 8 SDK. We'd like to deploy to iOS 7 as well. Is that possible? When we set the deployment target of the project to 7.0, we get compile time errors like this:We are creating an app using Xcode 6 beta 5 + S