在表内使用bootstrap 3弹出窗口，按钮顶部不显示

<link rel="stylesheet" href="https://cdn.bootcss.com/bootstrap/3.3.7/css/bootstrap.min.css">
<script src="https://cdn.bootcss.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>

<table>
  <tr>
    <td>
      <button type="button" class="btn btn-primary" id="myButton">点击弹出窗口</button>
    </td>
  </tr>
</table>

<script>
  $(document).ready(function() {
    $('#myButton').click(function() {
      $('#myModal').modal('show');
    });
  });
</script>

<div class="modal fade" id="myModal" tabindex="-1" role="dialog" aria-labelledby="myModalLabel">
  <div class="modal-dialog" role="document">
    <div class="modal-content">
      <div class="modal-header">
        <button type="button" class="close" data-dismiss="modal" aria-label="Close"><span aria-hidden="true">&times;</span></button>
        <h4 class="modal-title" id="myModalLabel">弹出窗口标题</h4>
      </div>
      <div class="modal-body">
        弹出窗口内容
      </div>
      <div class="modal-footer">
        <button type="button" class="btn btn-default" data-dismiss="modal">关闭</button>
        <button type="button" class="btn btn-primary">保存</button>
      </div>
    </div>
  </div>
</div>