title: Adding constraints in SDCAlertView
body: <p>I'm using a the pod SDCAlertView, I need to add an imageView + a textField to my content view, however I am having trouble with my constraints, below is my code.</p>
  
  <pre><code>let imageView = UIImageView(frame: CGRectMake(0, 0, 100, 100))
  imageView.image = UIImage(named: "kalafina")
  imageView.contentMode = .ScaleAspectFill
  let alert = AlertController(title: "Testing", message: "1234")
  imageView.translatesAutoresizingMaskIntoConstraints = false
  alert.contentView.addSubview(imageView)
  
  
  let imageHeightConstraint = NSLayoutConstraint(item: imageView, attribute: .Height, relatedBy: .Equal, toItem: nil, attribute: .NotAnAttribute, multiplier: 1.0, constant: 100)
  let imageWidthConstraint = NSLayoutConstraint(item: imageView, attribute: .Width, relatedBy: .Equal, toItem: nil, attribute: .NotAnAttribute, multiplier: 1.0, constant: 100)
  let imageCenterXConstraint = NSLayoutConstraint(item: imageView, attribute: .CenterX, relatedBy: .Equal, toItem: alert.contentView, attribute: .CenterX, multiplier: 1.0, constant: 0.0)
  let imageTopConstraint = NSLayoutConstraint(item: imageView, attribute: .Top, relatedBy: .Equal, toItem: alert.contentView, attribute: .Top, multiplier: 1.0, constant: 0)
  let imageBottomConstraint = NSLayoutConstraint(item: imageView, attribute: .Bottom, relatedBy: .Equal, toItem: alert.contentView, attribute: .Bottom, multiplier: 1.0, constant: 0)
  alert.view.addConstraint(imageTopConstraint)
  alert.view.addConstraint(imageBottomConstraint)
  alert.view.addConstraint(imageHeightConstraint)
  alert.view.addConstraint(imageWidthConstraint)
  alert.view.addConstraint(imageCenterXConstraint)
  
  alert.addAction(AlertAction(title: "Cancel", style: .Preferred))
  alert.addAction(AlertAction(title: "Ok", style: .Default, handler: { action in
  
      print("Sending")
  
  }))
  alert.present()
  </code></pre>
  
  <p>This is my result<a href="https://i.stack.imgur.com/ijA5c.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ijA5c.png" alt="enter image description here"></a></p>