/ navigation styled for Bootstrap 4.0 .container

nav.navbar.navbar-dark.bg-inverse
  ul.nav.navbar-nav.clearfix
    li.nav-item
      button.navbar-toggler.hidden-sm-up.nav-link aria-controls="exCollapsingNavbar2" aria-expanded="false" aria-label=("Toggle navigation") data-target="#exCollapsingNavbar2" data-toggle="collapse" type="button"
        | ☰
  #exCollapsingNavbar2.collapse.navbar-toggleable-xs
    = link_to "Rails bootstrap", root_path, class: 'navbar-brand'
    ul.nav.navbar-nav
      = render 'layouts/navigation_links'