Fix Missing ItemMaps when Handling Drag Event in Peek Mode

PeekInterceptor suffered from refactoring that removed hit area,
by relying on the current item map, which may not exist at time of
event handling if scrolling beyond the pre-rendered range.

Fix by relying on the AwesomeMap associated with the interceptor,
which will always be available.
Merge branch 'fix_uncleared_content_bug_in_item_maps' into fix_missing_item_map_when_handling_drags_in_peek_interceptor
Adding some off-by-one guards
Adding unit tests
Lint screener
Merge pull request #81 from WebFilings/fix_ninja_scroll_freakout

Fix ninja scroll freakout