variable based transition mixin

variable based transition mixin

//usage: @include shift([property],[duration],[easing]);
@mixin shift($property: all, $duration: $transitionSpeed, $ease: $easingFunction){
  -webkit-transition: $property $duration $ease;
  -moz-transition: $property $duration $ease;
  -o-transition: $property $duration $ease;
  transition: $property $duration $ease;
}