title: jQPlot - remove vertical grid lines
body: <p>I am using jqPlot as my charting framework and have numerous charts in my application, primarily line and stacked bar charts. </p>
  
  <p>I now have a requirement to only show the horizonal grid lines on these charts and do not see any options in jqPlot to do this.</p>
  
  <p>There is a <code>showGridline</code> option but that disables the grid lines entirely. </p>
  
  <p>Is it possible to remove only the vertical grid lines in jqPlot and continue to show the horizontal ones?</p>