bootstrap: Can't create a navbar?

bootstrap: Can't create a navbar?

I am using twitter bootstrap v3 to create a navbar and I follow their
documentation
<div class="navbar">
<div class="navbar-inner">
<div class="container">
<a class="brand" href="/">Title</a>
<ul class="nav">
<li><a href="/about">About</a></li>
<li><a href="/feedback">Feedback</a></li>
<li><a href="/me" target="_blank">whoami</a></li>
</ul>
</div>
</div>
</div>
But the navbar is not created. Here is the demo
What is that I am missing here?