title: Validate at least one checkbox is checked with jQuery Validator
body: <p>All,
  I'm trying to make sure at least one of my checkboxes is checked with jQuery Validator before I allow the user to submit the form. If I have the following code for my checkboxes:</p>
  
  <pre><code>&lt;input type="checkbox" value="23" class="select" name="vendor_categories[]"&gt;&amp;nbsp;Test1&lt;br /&gt;
  &lt;input type="checkbox" value="8" class="select" name="vendor_categories[]"&gt;&amp;nbsp;Test2&lt;br /&gt;
  &lt;input type="checkbox" value="9" class="select" name="vendor_categories[]"&gt;&amp;nbsp;Test3&lt;br /&gt;
  &lt;input type="checkbox" value="2" class="select" name="vendor_categories[]"&gt;&amp;nbsp;Test4&lt;br /&gt;
  </code></pre>
  
  <p>Then I have the following jQuery code:</p>
  
  <pre><code>$("#register_vendor").validate({
      ignore: "",
      rules: {
          vendor_email: {
              required: true,
              email: true
          },
          vendor_name: "required",
          zip: {
              required: true,
              digits: true,
              minlength: 5
          }
      },
      messages: {
          vendor_email: {
              required: "&lt;br&gt;Please enter an email address!&lt;br&gt;&lt;br&gt;",
              email: "&lt;br&gt;Please enter a valid email address!&lt;br&gt;&lt;br&gt;"
          },
          vendor_name: "&lt;br&gt;Please enter your vendor name!&lt;br&gt;&lt;br&gt;",
          zip: {
              required: "&lt;br&gt;Please enter a zip code!&lt;br&gt;&lt;br&gt;",
              digits: "&lt;br&gt;You can only enter in numbers for the zipcode!&lt;br&gt;&lt;br&gt;",
              minlength: "&lt;br&gt;The zip code has to be atleast 5 digits!&lt;br&gt;&lt;br&gt;"
          }
      },
      invalidHandler: function(e, validator) {
          var errors = validator.numberOfInvalids();
          if (errors) {
              var message = errors == 1
                  ? 'You missed 1 field. It has been highlighted below'
                  : 'You missed ' + errors + ' fields.  They have been highlighted below';
              alert(message);
          }
          $('.togDesc').show();
      }
  });
  </code></pre>
  
  <p>How would I got</p>