Merged experimental-shadow to add inner shadow to the ParallaxHeaderView

commit a0745651b12b70f8365d5985829b643d5fef931a
Author: Mathias Amnell <mathias@apping.se>
Date:   Mon Apr 15 08:41:05 2013 +0200

    Added a shadow view to the bottom of the APParallaxView

commit b674ede313ea00b13589cd00a57f08d6e5e63017
Author: Mathias Amnell <mathias@apping.se>
Date:   Sun Apr 14 23:23:37 2013 +0200

    Began some experiments with shadow
Updated podspec and readme to version 0.1.3