Updated xcode and swift version requirements

Author: AlexLittlejohn

README.md

@@ -17,7 +17,7 @@ A camera view controller with custom image picker and image cropping.
 - [x] Tap to focus
 
 ### Installation & Requirements
-This project requires Xcode 8.3 to run and compiles with swift 3.1
+This project requires Xcode 9 to run and compiles with swift 4
 > Note: This library makes use of the AVFoundation camera API's which are unavailable on the iOS simulator. You'll need a real device to run it.
 
 CocoaPods: