title: How to assign an error message when adding css class validation rule
body: <p>I have added a css class validation rule for jquery validator as follows:
  <code><pre>
  jQuery.validator.addClassRules({
          requiredDatepicker: {
              required: true,
              date: true
          }
      });
  </code></pre></p>
  
  <p>However, when doing this I get the default error messages.  How can I assign custom error messages when using addClassRules()?</p>