Created by: zalog
Change the .navbar-toggler to default contextual .navbar-*-color in case we use some other custom icons like .navbar-toggler-icon.fa.fa-search.
Please take a look at this demo: http://codepen.io/zalog/pen/MJLZOE/ - you must resize down the viewport.
Being on mobile, I'm not sure if we need a hover-focus mixin for .navbar-toggler, but if we do, please let me know.