Header: better handling of NaN dimensions
ImageLoader: saves texture frame for use in measurement instead of using width and height directly on texture because the frame may be bigger.
Header: vertical middle alignment accounts for padding
Label: exposes baseline
IGroupedListHeaderOrFooterRenderer: like the item renderer, must be IFeathersControl
ListDataViewPort, GroupedListDataViewPort: better disposal of item and header/footer renderers (sets owner and data to null)
ImageLoader: better texture and bitmapdata disposal.
Merge branch 'master' of git://github.com/joshtynjala/feathers