Improved performance in Stacked layout by hiding invisible items -- thanks to walsh2000 for the idea
Allow multiple items to overall at bottom in Exposed layout as suggested by walsh2000

* Added TGLExposedLayout property -bottomOverlapCount defaulting to 1
* Added TGLStackedViewController property -exposedBottomOverlapCount defaulting to 1, which is passed to -bottomOverlapCount above
* Improvement performance by properly hiding off-screen items
Minor clean-ups
Sample project shows 99 cards, now
Version bump to 1.0.4