nav.html

<nav class="navbar navbar-default">
    <div class="container-fluid">
        <div class="navbar-header">
            <button type="button" class="navbar-toggle collapsed" data-toggle="collapse"
                    data-target="#main-navbar" aria-expanded="false">
                <span class="sr-only">Toggle navigation</span>
                <span class="icon-bar"></span>
                <span class="icon-bar"></span>
                <span class="icon-bar"></span>
            </button>
            <a class="navbar-brand" href="#">Pet Clinic</a>
        </div>

        <div class="collapse navbar-collapse" id="main-navbar">
            <ul class="nav navbar-nav">
                <li><a href="#!/welcome">Home</a></li>

                <li class="dropdown">
                    <a href="javascript:void(0)" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="false">Owners <span class="caret"></span></a>
                    <ul class="dropdown-menu">
                        <li><a href="#!/owners">All</a></li>
                        <li><a href="#!/new-owner">Register</a></li>
                    </ul>
                </li>

                <li><a href="#!/vets">Vets</a></li>
            </ul>
        </div>
    </div>
</nav>