Improve walking-detecting
Refactor player.js - split classes into own files
Now players can drop (useless) bombs that never explodes
Let server track bombs
Extract CollisionEngine from server.js
Extract Bomb from server.js
Extract Client into own file. Also removed Bomb from server
Extract ClientManager from server.js
extract level from server
Simplified collision_engine
Let collision_engine use Point instead of x,y coordinates
More refactoring. Move player actions (movement, drop bomb) into own classes.

Drop bomb does not currently work (missing implementation)
Better isolation of nodejs/socket.io code and the game.
Simplify constructor of Client
Change method signature for actions
level.getJson() returns source json data
Simplify client.js - move protocol logic into Protocol. Much nicer
Made protocol indenpendent of client. Adds support for dropping bombs