replaced connection object with a user object (that contains a
connection object)
modified sendPublicMessageResponse method to send to every user in the
room
modified sendJoinRoomSuccessResponse to send the response to every user
in the room. modified the sendJoinRoomFailure to send the error back to
the sender
modified method to send the LogoutResponse back to the sender
modified method to send the message to the target user
modified methods to send back the success or failure of the login
added UserManager and RoomManager fields, modified connected method to
create a new User for every new connection, modified the handler for
LoginRequest - added try/catch block for validating logins