title: UIProgressView with gradient
body: <p>Is there a way to make <code>progressTintColor</code> make a gradient one? Specifically I would like to make it a gradient color from green to red - standard temperature mode.</p>
  
  <p>Adding sublayer didn't work as it put the layer "behind" the view:</p>
  
  <pre><code>CAGradientLayer *gradient = [CAGradientLayer layer];
  gradient.frame = self.testBar.bounds;
  gradient.colors = [NSArray arrayWithObjects:(id)[[UIColor greenColor] CGColor], (id)[[UIColor redColor] CGColor], nil];
  [self.testBar.layer insertSublayer:gradient atIndex:0];
  </code></pre>