title: altFormat not working in jQuery datepicker input field
body: <p>I have date field (id begin-date)</p>
  
  <pre><code>$( "#begin-date" ).datepicker({ 
    minDate: -20,
    maxDate: "+1M +10D",
    dateFormat: "yy-mm-dd",
    altFormat: "yymmdd"
  });
  </code></pre>
  
  <p>On post, it prints the format as yy-mm-dd (2010-12-08), when it should print as yymmdd (20101208)</p>
  
  <p>Any ideas of why it is not posting it properly with altFormat set?</p>
  
  <p>input field rendered:</p>
  
  <pre><code>&lt;input type="text" name="begin_date" id="begin-date" class="validate[required]" value="" /&gt;
  </code></pre>