Abstract out key function call in KeyManager
Can bind keys to functions with arity > 0
Rename public methods in Puzzle API
Internal renaming in Puzzle.getNextClueNumber
Add remainOnThisClue to Puzzle.getNextSquareInDirection and dependents
Add remainOnThisClue argument to PuzzleManager.backspace
Turn on remainOnThisClue for backspace by default
Merge branch 'keys' into coffeescript-rewrite