code: function getFolders(dir) {
    try {
      return fs.readdirSync(dir)
        .filter(function (file) {
          return exports.isDirectory(path.join(dir, file));
        });
    } catch (ex) {
      return [];
    }
  }
docs: Get folder names.
  
  Should only occur once per directory.
  
  @param  {string} dir enclosing folder
  @return {[]}     array of folder names