code: function readApi(file, fn) {
    var ext = path.extname(file);
    if ('.js' === ext || '.ts' === ext) {
      readJsDoc(file, fn);
    } else if ('.yml' === ext) {
      readYml(file, fn);
    } else if ('.coffee' === ext) {
      readCoffee(file, fn);
    } else {
      throw new Error('Unsupported extension \'' + ext + '\'');
    }
  }
docs: Read API from file
  @api    private
  @param  {String}   file
  @param  {Function} fn