public void Unregister(IUser user, IBotUser botUser, String username, String password)
{
if(!botUser.Username.Equals(username))
throw new ArgumentException("Incorrect username.", "username");
if(!botUser.CheckPassword(password))
throw new ArgumentException("Incorrect password.", "password");
_identifiedUsers.Remove(user);
_users.Remove(botUser.Username);
}
