twitter bootstrap: selectpicker

HTML

<link rel="stylesheet" href="http://getbootstrap.com/2.3.2/assets/css/bootstrap.css">
<link rel="stylesheet" href="http://getbootstrap.com/2.3.2/assets/css/bootstrap-responsive.css">
<script src="http://getbootstrap.com/2.3.2/assets/js/bootstrap.js"></script>
<link rel="stylesheet" href="http://silviomoreto.github.io/bootstrap-select/stylesheets/bootstrap-select.css">
<script src="http://silviomoreto.github.io/bootstrap-select/javascripts/bootstrap-select.js"></script>
<select id="id_select" class="selectpicker">
        <option>cow</option>
        <option>aaa</option>
</select>

JavaScript

$(function() {
$('.selectpicker').selectpicker();
};