code: function watch (glob, watchOpt) {
      if (!started) {
        deferredWatch = emitter.watch.bind(null, glob, watchOpt)
      } else {
        // destroy previous
        if (fileWatcher) fileWatcher.close()
        glob = glob && glob.length > 0 ? glob : defaultWatchGlob
        glob = Array.isArray(glob) ? glob : [ glob ]
        watchOpt = xtend({ poll: opts.poll }, watchOpt)
  
        fileWatcher = createFileWatch(glob, watchOpt)
        fileWatcher.on('watch', emitter.emit.bind(emitter, 'watch'))
      }
      return emitter
    }
docs: enable file watch capabilities