title: PhantomJS , device size is always 1024
body: <p>I am unable to change the device size from 1024.<br>
  When setting:</p>
  
  <pre><code>page.viewportSize = { width: 1366, height: 768 };
  </code></pre>
  
  <p>I am still getting 1024, after </p>
  
  <pre><code>var width = page.evaluate(function(){
      return window.screen.width;
  }
  </code></pre>
  
  <p>This can be a serious issue, since some media queries are invovled.<br>
  Thanks.</p>