title: Possible to use xAxis with type "datetime" and yAxis with categories?
body: <p>I have a very simple example using Highcharts which uses "datetime" on one axis and categories on the other.  It renders with no points and does not show the categories labels at all.  I'm wondering now if you can't use that combination of types.  Here is the code:</p>
  
  <pre><code>var chart = new Highcharts.Chart({
      chart: {
        renderTo: 'container'
      },
      xAxis: {
        type: 'datetime'
      },
      yAxis: {
        categories: ['p1', 'p2']
      },
      series: [{
        type: 'scatter',
        data: [
          {
            name: 'Deliv1',
            x: Date.UTC(2011,0,1),
            y: 'p1'
          },
          {
            name: 'Deliv2',
            x: Date.UTC(2012,0,1),
            y: 'p2'
          }
        ]
      }]
    });
  </code></pre>