Added 4 UIViews instead of images and bounce method using UIKit Dynamics...

In certain situations a `UIView` object is much more customizable than an UIImage. A customizable option is added to `MCSwipeTableViewCell` to add four `UIView objects` instead of images. Also, a bounce method is added, to have the ability to show user the swipable cells. Bounce uses UIKit Dynamics so it is iOS 7 only.