Select2 append</label>
        <div class="controls">
          <div class="input-append">
            <select id="single-append" class="select2" style="width:400px;">
              <option></option>
              <option value="A">A</option>
              <option value="B">B</option>
              <option value="C">C</option>
            </select>
            <button class="btn" type="button" data-select2-open="single-append">
              <i class="icon-search"></i>
            </button>
          </div>