code: function addWatcher(dirPath) {
      Debug._l(dirPath);
      /*fs.watchFile(dirPath, function (curr, prev) {
       //        console.log('the current mtime is: ' + curr.mtime);
       //        console.log('the previous mtime was: ' + prev.mtime);
  
       generateCache(id, dirPath);
       });*/
      var watch = Watcher(dirPath, function (filePath, isModified, isDeleted) {
          if (isModified) {
              Debug._l(generateIdFromFilePath(filePath));
              generateCache(filePath);
          }
          if (isDeleted) {
              removeCache(generateIdFromFilePath(filePath));
          }
      });
  
      return watch;
  }
docs: watch a directory for changes
  @param id
  @param dirPath