Added realtime support, implemented using socket.io. Tree and user pin updates are now sent to connected clients in real time and with minimal changes across the wire. Clients that reconnect to the server after a period containing missed updates automatically re-sync to the current version, also with minimal changes across the wire.
Added versioning at the tree level; this makes it inexpensive to calculate the minimal set of node updates to send to a client to bring it from one version of the tree to the latest.
Version label in the web client now links to wildcodemonkey.com to provide a change log.