[RFC] Added scssMap template for sass 3.3+

I quickly threw this scss template for sass 3.3+ together that takes advantage of the new sass maps. This still requires a bit more testing in production. What do you think is this something that could be added or even replace the existing scss template?

Example Output:

``` scss
@function sprite($sprite, $attribute) {
    @return map-get(map-get($sprites, $sprite), $attribute),
}

$sprites: (
    remove: (
        x: 0px,
        y: 0px,
        offset_x: 0px,
        offset_y: 0px,
        width: 10px,
        height: 11px,
        total_width: 10px,
        total_height: 233px,
        image: 'icon-sprite.png'
    ),
    remove_active: (
        x: 0px,
        y: 111px,
        offset_x: 0px,
        offset_y: -111px,
        width: 10px,
        height: 11px,
        total_width: 10px,
        total_height: 233px,
        image: 'icon-sprite.png'
    ),
    remove_hover: (
        x: 0px,
        y: 222px,
        offset_x: 0px,
        offset_y: -222px,
        width: 10px,
        height: 11px,
        total_width: 10px,
        total_height: 233px,
        image: 'icon-sprite.png'
    ),
);

@mixin spriteWidth($sprite) {
  width: sprite($sprite, 'width');
}

@mixin spriteHeight($sprite) {
  width: sprite($sprite, 'height');
}

@mixin spritePosition($sprite) {
  background-position: sprite($sprite, 'offset_x') sprite($sprite, 'offset_y');
}

@mixin spriteImage($sprite) {
  background-image: url(sprite($sprite, 'image'));
}

@mixin sprite($sprite) {
  @include spriteImage($sprite);
  @include spritePosition($sprite);
  @include spriteWidth($sprite);
  @include spriteHeight($sprite);
}
```

Example Usage:

List all sprites as icons:

``` scss
@each $sprite, $attributes in $sprites {
    .Icon--#{$sprite} {
        @include sprite($sprite);
    }
}
```

Create single sprite:
``` scss   
.Icon--remove {
    @include sprite('remove');
}
```