Adds the navbar to the application layout

building-info adding navbar to application layout.erb

...
<nav class="navbar">
   <div class="navbar-menu">
     <div class="navbar-start">
       <%= link_to 'Districts', districts_path, class: "navbar-item" %>
       <%= link_to 'Buildings', buildings_path, class: "navbar-item" %>
     </div>
   </div>
</nav>

<%= yield %>
...