title: Title for iframe/video in magnific popup
body: <p>I need to show title/caption for video popup. In image type there is option for this, but none for video/iframe.</p>
  
  <p>In docs (<a href="http://dimsemenov.com/plugins/magnific-popup/documentation.html#iframe_type">http://dimsemenov.com/plugins/magnific-popup/documentation.html#iframe_type</a>) I found example of templating markup but I don't understand how to make title visible.</p>
  
  <p>Would you please help me to setup iframe markup to show title in popup window from link like</p>
  
  <pre><code>&lt;a class="popup" title="This is caption" href="http://vimeo.com/41128754"&gt;&lt;/a&gt;
  </code></pre>
  
  <p>JS code</p>
  
  <pre><code>    $('a.popup').magnificPopup({
          disableOn: 700,
          type: 'iframe',
          mainClass: 'mfp-fade',
          removalDelay: 160,
          preloader: false,
          fixedContentPos: true,
          titleSrc: 'title'
  
      });
  </code></pre>
  
  <p>Thank you.</p>