Examples

        <%= navbar header => ['The brand', ['#'], hamburger, toggler => 'bs-example-navbar-collapse-1'], [] %>

        <nav class="navbar navbar-default">
            <div class="container-fluid">
                <div class="navbar-header">
                    <button class="collapsed navbar-toggle" data-target="#bs-example-navbar-collapse-1" data-toggle="collapse" type="button">
                        <span class="icon-bar"></span>
                        <span class="icon-bar"></span>
                        <span class="icon-bar"></span>
                    </button>
                    <a class="navbar-brand" href="#">The brand</a>
                </div>
            </div>
        </nav>

        <%= navbar html_header => qq{
                <div class="navbar-header">
                    <button class="collapsed navbar-toggle" data-target="#bs-example-navbar-collapse-1" data-toggle="collapse" type="button">
                        <span>Expand</span>
                    </button>
                    <a class="navbar-brand" href="#">The brand</a>
                </div>
        }, [] %>

        <nav class="navbar navbar-default">
            <div class="container-fluid">
                <div class="navbar-header">
                    <button class="collapsed navbar-toggle" data-target="#bs-example-navbar-collapse-1" data-toggle="collapse" type="button">
                        <span>Expand</span>
                    </button>
                    <a class="navbar-brand" href="#">The brand</a>
                </div>
            </div>
        </nav>

By using `html_header` you can specify an entirely customized header.

        <%= navbar inverse, header => ['The Brand', ['#'], hamburger, toggler => 'collapse-45821'],
                   [
                        form => [
                            [['/login'], method => 'post', left],
                            [
                                formgroup => [
                                    undef,
                                    text_field => ['search-term', placeholder => 'Search' ],
                                ],
                                submit_button => ['Submit'],
                            ]
                        ],
                        button => ['A link', ['#'], left ],
                        nav => [
                            [
                                ['Another linkage', ['#'] ]
                            ]
                        ],
                        p => ['Hello', right]
                   ]
        %>

        <nav class="navbar navbar-inverse">
            <div class="container-fluid">
                <div class="navbar-header">
                    <button class="collapsed navbar-toggle" data-target="#collapse-45821" data-toggle="collapse" type="button">
                        <span class="icon-bar"></span>
                        <span class="icon-bar"></span>
                        <span class="icon-bar"></span>
                    </button>
                    <a class="navbar-brand" href="#">The Brand</a>
                </div>
                <div class="collapse navbar-collapse" id="collapse-45821">
                    <form action="/login" class="navbar-form navbar-left" method="post">
                        <div class="form-group">
                            <input class="form-control" id="search-term" name="search_term" placeholder="Search" type="text" />
                        </div>
                        <button class="btn btn-default" type="submit">Submit</button>
                    </form>
                    <a class="btn btn-default navbar-btn navbar-left" href="#">A link</a>
                    <ul class="nav navbar-nav">
                        <li><a href="#">Another linkage</a></li>
                    </ul>
                    <p class="navbar-right navbar-text">Hello</p>
                </div>
            </div>
        </nav>