Adds scale method in Animation

[nefarianblack]

Adds a simple scale method:

static func scale(toX x: CGFloat, y: CGFloat, duration: TimeInterval = 0.3) -> Animation {
        return Animation(duration: duration) {
            $0.transform = CGAffineTransform(scaleX: x, y: y)
        }
    }

A bounce animation can be done as:

bounceView.animate(
    .scale(toX: 1.1, y: 1.1, duration: 1),
    .scale(toX: 0.95, y: 0.95, duration: 1),
    .scale(toX: 1.0, y: 1.0, duration: 1)
)