title: HTML custom attribute always return undefined in Jquery
body: <p>I have HTML element as below</p>
  
  <pre><code>&lt;input type="text" id="Search" select-box-search="true" select-box-search-url="testURL" /&gt; 
  </code></pre>
  
  <p>I have jQuery as below.</p>
  
  <pre><code> $(":input[select-box-search]").each(function () {
          $(this).autocomplete({
              source: function (request) {
                  var url = $(this).attr("select-box-search-url");
                  $.ajax({
                      async: false,
                      cache: false,
                      type: "POST",
                      url: url,
                      data: { "term": request.term},
                      success: function (data) {
  
                          }
                      }
                  });
              }
          });
      });
  </code></pre>
  
  <p>The "url" is always undefined. However "this" is referring to correct element (when debugged in Chrome). Anything missing?</p>
  
  <p>Alan</p>