Save descriptive output meta data to a JSON file.

def save_output_meta(self):
        """
        Save descriptive output meta data to a JSON file.
        """
        options = self.options
        file_path = os.path.join(options.outputdir, 'output.meta.json')
        with open(file_path, 'w') as outfile:
            json.dump(self.OUTPUT_META_DICT, outfile)