code: function addWatcher(dirPath) {
      Debug._l(dirPath);
      Watcher(dirPath, function (filePath, action) {
          switch (action) {
              case Watcher.ADD_EVENT:
              case Watcher.CHANGE_EVENT:
                  Debug._l(generateIdFromFilePath(filePath));
                  generateCache(filePath);
                  break;
  
              case Watcher.DELETE_EVENT:
                  removeCache(generateIdFromFilePath(filePath));
                  break;
  
          }
      });
  
  }
docs: watch a directory for changes
  @param dirPath