Parse message string to response object.

def parse(cls, msg):
        """Parse message string to response object."""
        lines = msg.splitlines()
        version, status_code, reason = lines[0].split()
        headers = cls.parse_headers('\r\n'.join(lines[1:]))
        return cls(version=version, status_code=status_code,
                   reason=reason, headers=headers)