Add quiz history widget functional that tracks last four challenges.
Added newline at end of files where missing.
Change look and feel of history widget by moving it just above answer box, and overlay history over progress bar to reduce clutter.
Add comment to explain z-index
Update background of history widget to contrast white of answer widget.
Switch to module system unreliant on window object, thereby increasing portability
Prune extra levels of indirection that appeared to be of questionably value as the app evolved. Also fix some minor code quality issues such as missing semicolons and newline at eof.
Add incomplete options page, also setup button to switch to the correct scenes.