Improve .sidebar-nav a Hover Animation

[mattrothenberg]

I think we can improve the animation on the .sidebar-nav a elements by transitioning both the box-shadow and padding properties instead of relying on the global transition: .4s which is currently in place.

As it stands, the border style that gets added on hover (border-left: 4px solid #1188ff) is causing the animation to be very laggy.

My proposal:

.sidebar-nav a {
    /* omitting other styles */
    box-shadow: none;
    transition: all .4s ease-out;

    &:hover {
        padding-left: 15px;
        box-shadow: inset 4px 0 0 #1188ff;
    }

}