title: Applying a Gradient to CAShapeLayer
body: <p>Does anyone have any experience in applying a Gradient to a CAShapeLayer? CAShapeLayer is a fantastic layer class, but it appears to only support solid fill coloring, whereas I'd like it to have a gradient fill (actually an animatable gradient at that). </p>
  
  <p>Everything else to do with CAShapeLayer (shadows, shapes, stroke color, animatable shape path) is fantastic.</p>
  
  <p>I've tried placing a CAGradientLayer inside a CAShapeLayer, or indeed setting the CAShapeLayer as the mask of the GradientLayer and adding both to a container layer, but these don't have the right outcome.</p>
  
  <p>Should I subclass CAShapeLayer, or is there a better way forward?</p>
  
  <p>Thanks.</p>