title: bootstrap dropdown 3.3.7 submenu does not expand
body: <p>I pasted the code from <a href="http://bootstrapessentials.com/fulldocs/components/navbar/navbar-submenu/" rel="nofollow noreferrer">here</a> into my web application. It works except for the
  <code>Service C</code> dropdown submenu. I can't see <code>Service C1</code> ... <code>Service C5</code>.</p>
  
  <pre><code>&lt;ul class="nav navbar-nav"&gt;
          &lt;li class="active"&gt;&lt;a href="#"&gt;Home&lt;/a&gt;&lt;/li&gt;
          &lt;li&gt;&lt;a href="#about"&gt;About&lt;/a&gt;&lt;/li&gt;
          &lt;li class="dropdown"&gt;
              &lt;a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="true"&gt; &lt;span class="nav-label"&gt;Services&lt;/span&gt; &lt;span class="caret"&gt;&lt;/span&gt;&lt;/a&gt;
              &lt;ul class="dropdown-menu"&gt;
                  &lt;li&gt;&lt;a href="#"&gt;Service A&lt;/a&gt;&lt;/li&gt;
                  &lt;li&gt;&lt;a href="#"&gt;Service B&lt;/a&gt;&lt;/li&gt;
                  &lt;li class="dropdown-submenu"&gt;
                      &lt;a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="false"&gt; &lt;span class="nav-label"&gt;Service C&lt;/span&gt;&lt;span class="caret"&gt;&lt;/span&gt;&lt;/a&gt;
                      &lt;ul class="dropdown-menu"&gt;
                          &lt;li&gt;&lt;a href="#"&gt;Service C1&lt;/a&gt;&lt;/li&gt;
                          &lt;li&gt;&lt;a href="#"&gt;Service C2&lt;/a&gt;&lt;/li&gt;
                          &lt;li&gt;&lt;a href="#"&gt;Service C3&lt;/a&gt;&lt;/li&gt;
                          &lt;li&gt;&lt;a href="#"&gt;Service C4&lt;/a&gt;&lt;/li&gt;
                          &lt;li&gt;&lt;a href="#"&gt;Service C5&lt;/a&gt;&lt;/li&gt;
                      &lt;/ul&gt;
                  &lt;/li&gt;
              &lt;/ul&gt;
          &lt;/li&gt;
      &lt;/ul&gt;
  </code></pre>
  
  <p>The page writes now:</p>
  
  <pre><code>The support for sub-menu was disabled in latest version of bootstrap. The option can be re-enabled by including a small CSS. 
  </code></pre>
  
  <p>Do you know the CSS that is needed and where to put it?</p>
  
  <p>I'm using bootstrap 3.3.7 and would like not to change this version.</p>