code: function getDirectories(dir, cb) {
    fs.readdir(dir, function(err, objects){
      if (err) { return cb && cb(err); }
  
      var dirs = objects.filter(function(item){
        return fs.statSync(path.join(dir, item)).isDirectory();
      });
  
      cb && cb(null, dirs)
    })
  }
docs: Get list of directories `dir` from asynchronously
  
  @param {String} dir
  @param {Function} cb