title: Error rendering react-bootstrap components
body: <p>I have recently migrated from using twitter-bootstrap in react classes to using react-bootstrap. I wanted to test out react-bootstrap Navbar. My code is as:</p>
  
  <pre><code>import React from 'react';
  import { Link } from 'react-router';
  import Radium from 'radium';
  import Grid from 'bootstrap-grid-react';
  import * as bootstrap from "react-bootstrap";
  
  
  export default class Layout extends React.Component {
  
      constructor() {
          super();
          this.state = {};
      }
  
      render() {
          let {Nav, Navbar, NavItem, NavDropdown, MenuItem} = bootstrap;
          return (
              &lt;div&gt;
                  &lt;Navbar&gt;
                      &lt;Navbar.Header&gt;
                        &lt;Navbar.Brand&gt;
                          &lt;a href="#"&gt;APITest&lt;/a&gt;
                        &lt;/Navbar.Brand&gt;
                      &lt;/Navbar.Header&gt;
                      &lt;Nav&gt;
                        &lt;NavItem eventKey={1} href="#"&gt;New user
                        &lt;/NavItem&gt;
                        &lt;NavItem eventKey={2} href="#"&gt;Create New User&lt;/NavItem&gt;
                        &lt;NavDropdown eventKey={3} title="Dropdown" id="basic-nav-dropdown"&gt;
                          &lt;MenuItem eventKey={3.1}&gt;Action&lt;/MenuItem&gt;
                          &lt;MenuItem eventKey={3.2}&gt;Another action&lt;/MenuItem&gt;
                          &lt;MenuItem eventKey={3.3}&gt;Something else here&lt;/MenuItem&gt;
                          &lt;MenuItem divider /&gt;
                          &lt;MenuItem eventKey={3.3}&gt;Separated link&lt;/MenuItem&gt;
                        &lt;/NavDropdown&gt;
                      &lt;/Nav&gt;
                  &lt;/Navbar&gt;
              &lt;/div&gt;
  
          )
      }
  }
  </code></pre>
  
  <p>However this gives me an error</p>
  
  <blockquote>
    <p>Uncaught Error: Invariant Violation: Element type is invalid:
    expected a string (for built-in components) or a class/function (for
    composite components) but got: undefined. Check the render method of
    <code>Layout</code>.</p>
  </blockquote>
  
  <p>and a warning:</p>
  
  <blockquote>
    <p>Warning: React.createElement: type should not be null, undefined,
    boolean, or number. It should be a string (for DOM elements) or a
    ReactClass (for composite components). Check the render method of
    <code>Layout</code>.</p>
  </blockquote>
  
  <p>I also tried using
  <code>import {Nav, Navbar, NavItem, NavDropdown, MenuItem} from 'react-bootstrap'</code> but it also won't work. There is definitely a problem in how I am using <code>Navbar</code> because a normal div is rendering just fine. </p>
  
  <p>Any help is really appreciated.</p>