title: Remove Class when reaching top of page?
body: <p>I am using the following script to add a drop shadow and position fixed to my header. However, when an user scrolls all the way back to the top how do I remove the class? </p>
  
  <p>Here my script: </p>
  
  <pre><code>$(function() {
   $(window).scroll(function() {
      var top_offset = $(window).scrollTop();
      if (top_offset) {
        $('.top_head_separator').addClass('fixed-top fade-in');
    }
  });
  </code></pre>
  
  <p>How do I reverse this when scroll bar is at very top?</p>