Rewrote most of it.. to accomplish #52
(also the old code been a lil dirty imo :))

Returns now a "meta" field instead of two - height and maxheight - fields.
The meta object contains these fields:
```
{
  maxHeight: int,
  maxWidth: int,
  images: [{
      height: int,
      offsetY: int,
      totalHeight: int,
      width: int
    },...]
}
```
Updates the generator functions to adopt the changes introduced to
the spriter script. See #52

Also did some cleanup to the output string building.