Made display utilities responsive (e.g., .d-none and d-{sm,md,lg,xl}-none).
Dropped the bulk of .hidden-* utilities for new [display utilities]((/docs/4.0/utilities/display/). For example, instead of .hidden-sm-up, use .d-sm-none. Renamed the .hidden-print utilities to use the display utility naming scheme. More info under the Responsive utilities section of this page.
Added .float-{sm,md,lg,xl}-{left,right,none} classes for responsive floats and removed .pull-left and .pull-right since they’re redundant to .float-left and .float-right.
<transition name="fade" mode="out-in">
<router-view></router-view>
</transition>