title: Value of type 'UIImageView' has no member 'fadeIn'
body: <p>Currently working on making an image fade in and out. I created two functions 'fadeIn' and 'fadeOut' they seem right to me but I can't seem to get them working. I keep getting Value of type 'UIImageView' has no member 'fadeIn'.</p>
  
  <pre><code>var imageView : UIImageView!
  
      override func viewDidLoad() {
          super.viewDidLoad()
          // Do any additional setup after loading the view, typically from a nib.
  
          imageView = UIImageView(frame: CGRect(x: 0, y: 0, width: 100, height: 100))
          imageView.contentMode = .scaleAspectFit
          imageView.center = self.view.center
          imageView.image = image
          self.view.addSubview(imageView)
          imageView.isHidden = true
          imageView.alpha = 0
          imageView.fadeIn()
  
          func fadeIn(withDuration duration: TimeInterval = 1.0) {
              UIImageView.animate(withDuration: duration, animations: {
                  self.imageView.alpha = 1.0
              })
          }
          func fadeOut(withDuration duration: TimeInterval = 1.0) {
              UIImageView.animate(withDuration: duration, animations: {
                  self.imageView.alpha = 0.0
              })
          }
  </code></pre>