title: Get attribute of selected <option> in ddSlick dropdown
body: <p>I am using your ddslick plugin with select element. </p>
  
  <pre><code>&lt;select name="category" id="cat"&gt;
      &lt;option cat_type="2" value="cat1" id="hello"&gt;Category1&lt;/option&gt;
      &lt;option cat_type="1" value="cat2" id="hello2"&gt;Category2&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>In here when select category I need to get selected value <strong>cat_type</strong>. I tried as below.</p>
  
  <pre><code>$('#cat').ddslick({
      width: "100%",
      onSelected: function (data) {
          console.log(data.selectedData);    
      }
  }); 
  </code></pre>
  
  <p>OUTPUT </p>
  
  <pre><code>Object { text="Category1", value="cat1", selected=true, more...}
  </code></pre>
  
  <p>But <strong>cat_type</strong> attribute is not there. Please help me If someone have experience with <strong>ddslick</strong> plugin.</p>
  
  <p>I have Inspect the html source for the select tag. but It doesn't contain that attribute.</p>
  
  <pre><code>&lt;div id="cat" class="dd-container" style="width: 100%;"&gt;
     &lt;div class="dd-select" style="width: 100%; background: none repeat scroll 0% 0% rgb(238, 238, 238);"&gt;
       &lt;input type="hidden" class="dd-selected-value" value="cat2"&gt;&lt;a class="dd-selected"&gt;
       &lt;label class="dd-selected-text"&gt;Category2&lt;/label&gt;&lt;/a&gt;&lt;span class="dd-pointer dd-pointer-down"&gt;&lt;/span&gt;
   &lt;/div&gt;
  
   &lt;ul class="dd-options dd-click-off-close" style="width: 100%; display: none;"&gt;
      &lt;li&gt;&lt;a class="dd-option"&gt; &lt;input type="hidden" value="cat1" class="dd-option-value"&gt; &lt;label class="dd-option-text"&gt;Category1&lt;/label&gt;&lt;/a&gt;
      &lt;/li&gt;
      &lt;li&gt;&lt;a class="dd-option dd-option-selected"&gt; &lt;input type="hidden" value="cat2" class="dd-option-value"&gt; &lt;label class="dd-option-text"&gt;Category2&lt;/label&gt;&lt;/a&gt;
     &lt;/li&gt;
  &lt;/ul&gt;
  </code></pre>
  
  <p></p>