If username not set and page is not login, then redirect to login page to ask user to introduce himself.
User delete on socket disconnection.
Remove undefined entry from users array
Message style changes.
Unused rules removed.
Redirect user to login page if not already logged in.
Broadcast on new user joining so other users get notified.
Add inline message note on new user join.
Broadcast on user left the chat so other users get notified.
Add inline message note when user left the chat.