title: jqplot show highlighter on only one chart
body: <p>I have a jqplot chart with two data lines. Only one should have the highlighter enabled.
  I tried this:</p>
  
  <pre><code>series:[
      {
          highlighter: {
              formatString: "",
              show: false
          }
      },
      {
          highlighter: {
              formatString: "Day %s: %d",
              show: true
          }
      }
  ]
  </code></pre>
  
  <p>But unfortunately, this doesn't work: the highlighter shows a small empty dot at the first line, whereas it should show nothing.</p>
  
  <p>How do I show the highlighter on one chart and not on the other?</p>