title: Tickformatter not performing as expected in latest version of Flot
body: <p>In our previous version of Flot, the following tickformatter function worked fine. It displayed the value and used the class correctly.</p>
  
  <pre><code>yaxis: {
       tickFormatter: function(v, axis) {
          return "&lt;span class='axisLabel'&gt;" + v + "%&lt;/span&gt;";
       }
  </code></pre>
  
  <p>In the latest version (v. 0.7) it renders the  tags literally so next to the graph I see a something like
      <code>&lt;span class='axisLabel'&gt;50%&lt;/span&gt;</code>
  where the y axis tick labels should be. I should only be seeing a list of percentages.</p>
  
  <p>I've done as much debugging as I can but haven't found out what is causing this. Any ideas would be appreciated.</p>