title: how to add grid to table with pander?
body: <p>I am working with R, knitr and pander, and I can't find the option that would allow me to print a grid on a table with pander. 
  I tried :</p>
  
  <pre><code>pander(tableToPrint, style='grid') 
  </code></pre>
  
  <p>but it doesn't do anything, neither with this option or with 'multiline', 'rmarkdown'... I always get an horizontal line, then the column names, another horizontal line, all my data and an horizontal line. I would like to have an horizontal line between every line. Another option would be to alternate row colors.</p>