title: Adjust vertical position of UIBarButtonItem title inside UIToolbar
body: <p>Is it possible to adjust the title of a <code>UIBarButtonItem</code> inside an <code>UIToolbar</code>? </p>
  
  <p>I've tried the following lines of code without success:</p>
  
  <pre><code>UIBarButtonItem.appearance().setTitlePositionAdjustment(UIOffset(horizontal: 30, vertical: 30), forBarMetrics: UIBarMetrics.Default)
  </code></pre>
  
  <p>And this one:</p>
  
  <pre><code>self.setTitlePositionAdjustment(UIOffset(horizontal: 30, vertical: 30), forBarMetrics: UIBarMetrics.Compact)
  </code></pre>