title: hidden-xs class in btn-group make a line break
body: <p>all btn's - in a line (<a href="http://bootply.com/100575" rel="nofollow">http://bootply.com/100575</a>)</p>
  
  <p>when I add hidden-xs into btn-group, it make new line break. (<a href="http://bootply.com/100574" rel="nofollow">http://bootply.com/100574</a>)</p>
  
  <p>I changed codes but I can not find how to make btn's in a line with hidden-xs.</p>
  
  <pre><code>&lt;div class="btn-group"&gt;
      &lt;a class="btn btn-default" href="./board.php?bo_table=qna&amp;amp;page=1"&gt;&lt;i class="fa fa-list"&gt;&lt;/i&gt;List&lt;/a&gt;
  &lt;/div&gt;
  &lt;div class="btn-group"&gt;
      &lt;a class="btn btn-default" href="./write.php?bo_table=qna"&gt;&lt;i class="fa fa-edit"&gt;&lt;/i&gt;Write&lt;/a&gt;
  &lt;/div&gt;
  &lt;div class="btn-group hidden-xs"&gt; &lt;!-- here... --&gt;
      &lt;a class="btn btn-default" href="javascript:select_delete();"&gt;Delete&lt;/a&gt;
      &lt;a class="btn btn-default" href="javascript:select_copy('copy');"&gt;Copy&lt;/a&gt;
      &lt;a class="btn btn-default" href="javascript:select_copy('move');"&gt;Move&lt;/a&gt;
  &lt;/div&gt;
  </code></pre>