code: function (directory, callback) {
          var that = this;
          fs.readdir(directory, function (err, files) {
              async.map(files, function langdir_iterator(file, next) {
                  file = path.join(directory, file);
                  fs.stat(file, function (err, stats) {
                      if (err || !stats.isDirectory()) return next(err);
                      var l = path.basename(file);
                      fs.readdir(file, function (err, files) {
                          if (err) return next(err);
                          async.map(files, function podir_iterator(file, next) {
                              file = path.join(directory, l, file);
                              fs.stat(file, function (err, stats) {
                                  if (err || !stats.isFile()) return next(err);
                                  that.loadLanguageFile(file, l, next);
                              });
                          }, next);
                      });
                  });
              }, function langdir_done(err, results) {
                  callback && callback(err);
              });
          });
      }
docs: loads all po files from a flat locale directory tree. -> LANGUAGE_NAME/domain.po eg. en/jsgettext.po de/jsgettext.po etc.