title: how to added placeholder for editable-select
body: <p>I need placeholder for editable-select in x-editable angularjs.</p>
  
  <pre><code>&lt;span editable-select="data.CenterId" e-name="CenterId" e-form="rowform"  e-placeholder="Select Center"  e-ng-options="s.Id as s.Name for s in locationListData.centerData" onbeforesave="checkCenter($data)"  &gt;
    {{ showCenter(data)}}
  &lt;/span&gt;
  </code></pre>