options参数设置
UIView.animateWithDuration(3, delay: 0, usingSpringWithDamping: 0.1, initialSpringVelocity: 1, options: nil, animations: {
self.blueSquare.center.x = self.view.bounds.width - self.blueSquare.center.x
}, completion: nil)
options参数设置为nil会出错
