WIP
WIP
Merge branch 'Gravity_fields' of https://github.com/ernestaszdanys/freefall into Gravity_fields

Conflicts:
	game/index.html
	game/js/body.js
	game/js/game.js
	game/js/index.js
	game/js/observable.js
	game/js/rendering.js
	game/js/shape.js