Update project settings to recommended settings for Xcode 5.1
Fix #24—Make SDCAlertViewWidth public
Fix #23—Give contentView property a meaningful intrinsic content size

To avoid having to add vertical hugging constraints to an alert’s contentView property every time, it now has an intrinsic content size that will automatically give it a "best-guess" height based on its subviews. Previous sizing of the contentView is still supported, and should even be backwards compatible.