title: Xcode 6 UIImageView will not scale correctly
body: <p>Please see screen shot of flower setup below. The flower image has been correctly loaded from an asset catalog and when the app is run on various simulators the correct pixel resolution is assigned to each device. My problem is how to get the flower image to be scaled (equally sized to fit) the same on each device ?? 
  I have learnt how to position the image to different positions using constraints and frames but the image never scales correctly - please see first pic
  <img src="https://i.stack.imgur.com/pCiTl.png" alt="enter image description here">         </p>
  
  <p>The following image is a mock up of what I want to be able to do (flower image scaled correctly on each device)</p>
  
  <p><img src="https://i.stack.imgur.com/5Hghk.png" alt="enter image description here"></p>