docs: function(file, expression, callback) {
      var obj = { file: file,
                  expression: expression,
                  callback: callback };
      watchList.push(obj);
      var watcher = chokidar.watch(obj.file, {persistent: true, ignoreInitial: true});
      if(obj.callback.add != undefined)
          watcher.on('add', wrapCallback(obj.callback.add, obj.expression));
      if(obj.callback.change != undefined)
          watcher.on('change', wrapCallback(obj.callback.change, obj.expression));
      if(obj.callback.unlink != undefined)
          watcher.on('unlink', wrapCallback(obj.callback.unlink, obj.expression));
      if(obj.callback.addDir != undefined)
          watcher.on('addDir', wrapCallback(obj.callback.addDir, obj.expression));
      if(obj.callback.unlinkDir != undefined)
          watcher.on('unlinkDir', wrapCallback(obj.callback.unlinkDir, obj.expression));
      if(obj.callback.error != undefined)
          watcher.on('error', wrapCallback(obj.callback.error, obj.expression));
      watchers.push(watcher);
  }