Variable height, first implementation.
More variable work.
Add demos.
Fix ending at exactly top/bottom.
Minor fixes.
Support for nested group array observation.
Interim checkpoint.
Interim commit.
Use flex order to reduce binding overhead. Add demo.
Remove flex, translate into position 1 frame after model set.
Add "load more" API and start of grid support.
Grouped grid, resize support. More demos.
Remove loadMore, use core-scroll-threshold instead. Bugfixes.
iOS glitch reduction, scoped models, above/below support, grid math bug fixes, resize logic start, new demos.
Fix resize. Fix iOS overscroll.
Remove static image from demo.
Fix array mutation.  Fix scroll to bottom of list.
Use 3d transform.
Highlight selected.
Major update, refactor, bug fixes, update to webcomponents.js.