Optional map function in Puzzle.getFarthestValidCellInDirection
Implement option+backspace/delete (Mac) and ctrl+backspace/delete (Win)
Fake do-while loop for getFarthestValidCellInDirection
Add PuzzleManager.currentCell method
Avoid arguments splat
Merge branch 'erase-word' into keys

Conflicts:
	client/static/js/puzzlemanager.coffee