CANCELLED: Consolidate the playerListChange and updateState events

[LearningNerd]

The server never emits the playerListChange and updateState events separately; they always occur together, and only in two places: when new users log in, and when users disconnect from the server.

[LearningNerd]

Merging this into issue #16 ("Simplify the game state data model and events on client and server") and closing it!