Xcode 6.3 fabsf fixes

Shuts up a few warnings.

Storyboard support + bug fixes

• Added support for storyboards (Addresses #13)
• Fixed issue with buttons appearing under cell when cell is selected (Addresses #12)
• Added workaround for issues with accessoryType (Addresses #14)
• Fixed issue with translation vs. velocity (Addresses #16)

iOS 8 + Any Button support

• Better iOS 8 + UINavigationController popGestureRecognizer support. (Thanks, @mergesort!)
• Support for any button rather than just tinted buttons (Thanks, @Krivoblotsky!)