[examples] class="i-bar" should be class="icon-bar" in the btn-navbar

Created by: clayheaton

In the examples, the following code is used in the nav bar:

      <a class="btn btn-navbar" data-toggle="collapse" data-target=".nav-collapse">
        <span class="i-bar"></span>
        <span class="i-bar"></span>
        <span class="i-bar"></span>
      </a>

The images do not appear in the button that expands the navigation on narrow screens. The correct code is:

      <a class="btn btn-navbar" data-toggle="collapse" data-target=".nav-collapse">
        <span class="icon-bar"></span>
        <span class="icon-bar"></span>
        <span class="icon-bar"></span>
      </a>