title: Set an action for a teacup styled button in ruby motion
body: <p>if i am creating my button in my pro-motion screen:</p>
  
  <pre><code>add button = UIButton.new,
    stylename: :my_button,            # Teacup
    resize: [ :left, :right, :top ], # ProMotion
    frame: CGRectMake(25, 250, 90, 90)
  </code></pre>
  
  <p>How can I add an action to my button?</p>
  
  <p>The action should look something like this:</p>
  
  <pre><code>addTarget(self, action: :an_action,
                      forControlEvents:UIControlEventTouchUpInside)
  </code></pre>