Updated sample and demo GIF, FAB uses elevation on API 21+, support for RecyclerView

My previous pull request for RecyclerView support was replaced with this one. I also updated the sample to use AppCompat, so Material theming is used (and supports KitKat and below); the demo GIF was updated to reflect that. The FAB will use the elevation API for the shadow effect instead of the shadow drawable on Lollipop and above.