title: Using a <select multiple> to filter divs
body: <p>Say I have  like: </p>
  
  <pre><code>&lt;div class="numbers one two three"&gt;...&lt;/div&gt;
  &lt;div class="numbers one three five"&gt;...&lt;/div&gt;
  &lt;div class="numbers two four six"&gt;...&lt;/div&gt;
  &lt;div class="numbers one two four"&gt;...&lt;/div&gt;
  </code></pre>
  
  <p>and I have a select like:</p>
  
  <pre><code>&lt;select id="filternumbers" multiple="multiple"&gt;
      &lt;option value="one"&gt;One&lt;/option&gt;
      &lt;option value="two"&gt;Two&lt;/option&gt;
      &lt;option value="three"&gt;Three&lt;/option&gt;
      &lt;option value="four"&gt;Four&lt;/option&gt;
      &lt;option value="five"&gt;Five&lt;/option&gt;
      &lt;option value="six"&gt;Six&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>How do I get the select to filter divs based on my selection, say "two" and "four" - meaning only last two divs should be visible? </p>
  
  <p>I know I can do this for single select menus: </p>
  
  <pre><code>$('#filternumbers').on('change', function () {
      var number = $(this).val();
      $(".numbers").hide();
      $(".numbers").hasClass(number).show();
  });
  </code></pre>
  
  <p>But how do I do it for a multi select?</p>