Added iPhone 6, updated iPad Air, updated readme for Xcode 6, recompiled

This update includes the following:
-Added iPhone 6 vertical and landscape imagery with conditional statements
-Updated iPad Air to 2nd Generation imagery
-Updated readme to reflect Xcode 6.1 with iOS 8.1 simulator and newer overlay support
-Recompiled binary and zipped it up
-Included the source PSDs that were used to create the overlays