Socket.io interface for web browser, first sector map.

Added a sector map that works! So far, only player vessel and NPCs. Based on openlayers3 and hot-linked for now. Implemented client-side and server-side world model (although I'm not sure the server-side model is needed at all).

The javascript client receives the server packets via socket.io messages. It will add network traffic, but hey, it's simple and debuggeable.

Upgraded express.js dependency to 3.x in order to not have too many headaches with socket.io.

Updated a few fields and readme file.