title: Sticky header/admin bar issue
body: <p>I have a sticky nav bar on my WP site with a little script like this</p>
  
  <pre><code>jQuery(document).ready(function() {
      var wpAdminBar = jQuery('#wpadminbar');
      if (wpAdminBar.length) {
          jQuery("#site-navigation").sticky({
              topSpacing: wpAdminBar.height()
          });
      } else {
          jQuery("#site-navigation").sticky({
              topSpacing: 0
          });
      }
  });
  </code></pre>
  
  <p>But I noticed that my admin bar becomes un-stuck when the screen size is less than 600px so that it scrolls with the page, but because it's still actually on the screen it still adds the extra space above my navigation.</p>
  
  <p>Is there a different thing I should use besides .length or should I add in a check for screen width?</p>