Storyboard Support

[mac-gallagher]

The plan here is to add IBInspectable/IBDesignable support for both SwipeCard and SwipeCardStack so they work well with Storyboards. A similar enhancement was done here on my other repo MultiProgressView.

It would be great to add a new example using storyboards as well (again, check MultiProgressView for some inspo). Ideally, it would look like something that belongs in a production app!