title: Check if jquery plugin is loaded
body: <p>How can I check if this jquery plugin backstrech was already loaded:
  <a href="http://cdnjs.cloudflare.com/ajax/libs/jquery-backstretch/2.0.4/jquery.backstretch.min.js" rel="nofollow">http://cdnjs.cloudflare.com/ajax/libs/jquery-backstretch/2.0.4/jquery.backstretch.min.js</a></p>
  
  <p><code>if($.fn.backstretch)</code> is not working.</p>