created ThunderTank object (main game object),
added bullet collisions,
added map boundaries and obstacles,
created private variables in entites
updated README, added demo link
added (nodejs) express app
added multiplayer with socket.io
added Procfile for heroku
fixed package.json (removed trailing comma)
updated node port to use process.env.PORT or 5000
added Heroku Socket.IO configuration
added package.json engines (node and npm)