Fix fsnotify.Remove logic function.

[zhanluxianshen]

1 Use simple grammar in fsnotify package.

This makes checking events a lot easier; for example:

  if event.Op&Write == Write && !(event.Op&Remove == Remove) {
  }
Becomes:

  if event.Has(Write) && !event.Has(Remove) {
  }

According fsnotify notes

Fix Remove event.

[zhanluxianshen]

thanks.