make flexible col mixin

make-flexible-col.scss

@mixin make-col($ref, $margin, $col, $reverse: false) {
	$marginSum: $margin*($col - 1);
	$itemWidth: floor(($ref -$marginSum)/$col);
    width: percentage($itemWidth/$ref);

    @if ($reverse == true) {
	    float: right;
	    margin-left: percentage($margin/$ref);
	    &:last-child {
	        margin-left: 0;
	    }
    } @else {
	    float: left;
	    margin-right: percentage($margin/$ref);
	    &:last-child {
	        margin-right: 0;
	    }
    }
}