title: MutationObserver on span text change does not trigger
body: <p>This is just a boiled down example not an actual thing.</p>
  <p>Still MutationObserver isn't firing so my assumption on how it works is wrong.</p>
  <p><a href="http://jsfiddle.net/xqvbc43y/3/" rel="nofollow noreferrer">JSFiddle</a></p>
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="false" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>$(function() {
    var editButtonVisibility = function() {
      console.log('bam');
    }
  
    $('#RiskPostcodeSummary span').on("change", function() {
      console.log("pew pew");
    });
  
    var observer = new MutationObserver(function(e) {
      editButtonVisibility();
    });
  
    observer.observe($('#RiskPostcodeSummary span')[0], {
      characterData: true
    });
  });</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"&gt;&lt;/script&gt;
  &lt;div id="RiskPostcodeSummary"&gt;
    &lt;span&gt;&lt;/span&gt;
  &lt;/div&gt;
  &lt;input type="button" value="click" onClick="$('#RiskPostcodeSummary span').text('sdfsdf');" /&gt;</code></pre>
  </div>
  </div>
  </p>
  <p>Why isn't <code>MutationObserver</code> firing when I change text in <code>&lt;span&gt;</code>?</p>