Save the input meta data (options passed to the app) to a JSON file.

def save_input_meta(self):
        """
        Save the input meta data (options passed to the app) to a JSON file.
        """
        options = self.options
        file_path = os.path.join(options.outputdir, 'input.meta.json')
        with open(file_path, 'w') as outfile:
            json.dump(vars(options), outfile)