io.go
func (da *Cedar) Save(out io.Writer, dataType string) error {
	switch dataType {
	case "gob", "GOB":
		dataEecoder := gob.NewEncoder(out)
		return dataEecoder.Encode(da.cedar)
	case "json", "JSON":
		dataEecoder := json.NewEncoder(out)
		return dataEecoder.Encode(da.cedar)
	}
	return ErrInvalidDataType
}
func (da *Cedar) Save(out io.Writer, dataType string) error {
	switch dataType {
	case "gob", "GOB":
		dataEecoder := gob.NewEncoder(out)
		return dataEecoder.Encode(da.cedar)
	case "json", "JSON":
		dataEecoder := json.NewEncoder(out)
		return dataEecoder.Encode(da.cedar)
	}
	return ErrInvalidDataType
}
// Save saves the cedar to an io.Writer,
// where dataType is either "json" or "gob".