io.go
func (da *Cedar) LoadFromFile(fileName string, dataType string) error {
	file, err := os.OpenFile(fileName, os.O_RDONLY, 0600)
	defer file.Close()
	if err != nil {
		return err
	}
	in := bufio.NewReader(file)
	return da.Load(in, dataType)
}
func (da *Cedar) LoadFromFile(fileName string, dataType string) error {
	file, err := os.OpenFile(fileName, os.O_RDONLY, 0600)
	defer file.Close()
	if err != nil {
		return err
	}
	in := bufio.NewReader(file)
	return da.Load(in, dataType)
}
// LoadFromFile loads the cedar from a file,
// where dataType is either "json" or "gob".