boostrap3: navbar collapsed by default for all screen sizes.

navbar.sass

@media (max-width: 2000px)
  .navbar-header
    float: none
  .navbar-left, .navbar-right
    float: none !important
  .navbar-toggle
    display: block
  .navbar-collapse
    border-top: 1px solid transparent
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.1)
  .navbar-fixed-top
    top: 0
    border-width: 0 0 1px
  .navbar-collapse.collapse
    display: none !important
  .navbar-nav
    float: none !important
    margin-top: 7.5px
    > li
      float: none
      > a
        padding-top: 10px
        padding-bottom: 10px
  .collapse.in
    display: block !important