title: how sort numeric as text
body: <p>I have a column of years, but some are incomplete:</p>
  <pre>1860
  18--
  1945
  19--</pre>
  <p>tablesorter sorts them like this:</p>
  <pre>18--
  19--
  1860
  1945</pre>
  <p>Is there a class name I can use that will get them to sort correctly?</p>
  <pre>18--
  1860
  19--
  1945</pre>