Pass Nav props to ul so css classes can be applied

Per @pieterv https://github.com/react-bootstrap/react-bootstrap/issues/101#issuecomment-45953758
Couple of comments here:
The component JSX should be `<Nav className="pull-right" />` to keep things consistent.

Lets use `assert.ok(ReactTestUtils.findRenderedDOMComponentWithClass(instance, 'pull-right'));` for the assert like the other className checks in the file.

Think it might also be a good idea to duplicate these statements within this `it()` block with adding the `navbar` prop to the rendered component for the second assert since this behaviour changes depending on this.

Could you please check your whitespace here, looks like things aren't lining up.