Add keydown event handlers for left and right keys in SnakeBinder

	*also, put GameView render method in class definition,
	since we will only have one GameView
Add backbone library and underscore dependency

	* Practicing using backbone!
Add key bindings for moving the snake

	*Paired with Clark at Carbon 5 on this feature
	*Added updateSnakeDirection function to model
	*Added changeDirection in binder
Take away undeed comments and functions
Add isAlive attribute to snake model, prepare to change snake move

	*snake will now move by popping off the tail and drawing a new
	head, not by transforming every segment
	*isAlive will determine whether snake continues to move
Add methods so snake moves, eats, and grows!

	*SnakeModel eat() method adds a second tail so a tail remains
	after updatesnakeposition pops the tail off the top of the
	stack.
	* unshifting and popping off segments still a little wonky
	in the first three turns
	* Changed body array name to segments to avoid document.body
	confusion
	* got rid of useless and commented lines
Merge pull request #2 from mathildemouw/snake_death_observer

Snake death observer