[core] Implement pluggable support for item selection
[core] Update on-screen views on clearChoices() calls
[core] Change ItemSelectionSupport to always consume long clicks
[core] Move haptics/sound feedback to ItemClickSupport
[core] Use GestureDetectorCompat in ClickItemTouchListener
[readme] Update to match the state of the project
[readme] Some more tweaks and typo fixes
[readme] Remove redundant cautionary note
[readme] Add sample image
[images] Add sample image for README
[readme] A few more tweaks and fixes
[images] Resize sample image
[layouts] Account null item entries in list and grid layouts
[layout] Rename variables for clarity in BaseLayoutManager
[layouts] Properly allocate lane Rects when restoring state
[core] Change base SavedState to be Parcelable

Fixes #88
[layouts] Remove unused import from DividerItemDecoration
[layouts] Account for margins when drawing dividers

Fixes #94
[core] Remove unused imports from TwoWayLayoutManager
[sample] Add ability to add and remove items from adapter