title: Button autosize with auto layout in Xcode 6 w/ swift
body: <p>could anyone of you give me a hint, how to implement autosize of a button with auto-layout?</p>
  
  <p>To be more specific: 
  My button has 50x50px at iPhone 4s. How to implement this button, that its size increases on iPhone 6 plus screen resolution? Is there a kind of multiplier option? </p>
  
  <p>Edit: 
  I want, that the button w/ 50x50px on iPhone4s screen is increasing proportionally at iPhone5, iPhone6 display.</p>
  
  <p>Thanks. </p>
  
  <p>BR</p>