Updated Express 3 to Express 4

Doesn't work yet (port already used error) but can't tell if it's
server.js fault or my machine's.
Merge remote-tracking branch 'origin/dev' into node_update
Updated socket.io

Updated socket.io and made it compatible with Express 4, finally!

Final commit before merging with dev?
Merge remote-tracking branch 'origin/node_update' into dev