title: highcharts xAxis limit how far zoom in
body: <p>I have a highcharts graph where the X axis units is date.  My data is rounded to the nearest day, so there is no point zooming in beyond the day level.</p>
  
  <p>However, highcharts lets me zoom in to the hour level.  I don't want to let users zoom in any deeper than days.  So, I have defined my X axis as:</p>
  
  <pre><code> xAxis: {
          type: 'datetime',
          dateTimeLabelFormats: { // don't display the dummy year
              month: '%b \'%y',
              year: '%Y'               
          },
          minRange: 86400000                              
      },
  </code></pre>
  
  <p>yet I can still zoom in to the hour level.  I set minRange to 86400000 (i.e. 1 day) but it has no effect.  Am I setting the wrong thing?</p>