Improved GetImageSizeScaleTo

Added and changed the order of the view measurement.
You should always get the actual measure width and height of the view first, then fallback.

That way combining this with LayoutTree listeners you can wait for the view to be measured and 
your images are always scaled exactly to the view size
Merge pull request #191 from chrisjenx/patch-1

Improved getImageSizeScaleTo (consider measured View width and height)