Fix for issue #283

https://github.com/philsturgeon/codeigniter-restserver/issues/283
An example for this can be something like this:
    public function get_hashed_password($username) {
        $user = $this->ci->db->select($this->password_field . ' as password')->where($this->username_field, $username)->get($this->user_table);
        if ($user->num_rows() == 0) {
            return false;
        }

        $user_details = $user->row();
        $HA1 = $user_details->password;
        return $HA1;
    }