SASS mixin for shorthand position value. Only outputs the value specified. Usage `@include position( TOP, RIGHT, BOTTOM, LEFT );`

_position.scss

@mixin position( $top: null, $right: null, $bottom: null, $left: null ) {
    @if $top    { top: $top; }
    @if $right  { right: $right; }
    @if $bottom { bottom: $bottom; }
    @if $left   { left: $left; }
}