def update_from(user)
      @name = user.name
      @password = user.password
      @roster = user.roster.map {|c| c.clone }
    end
def update_from(user)
      @name = user.name
      @password = user.password
      @roster = user.roster.map {|c| c.clone }
    end
Update this user's information from the given user object.