code: @SafeVarargs
      public final static Observable<WatchEvent<?>> from(final File file, Kind<?>... kinds) {
          return from(file, null, kinds);
      }
docs: If file does not exist at subscribe time then is assumed to not be a
  directory. If the file is not a directory (bearing in mind the aforesaid
  assumption) then a {@link WatchService} is set up on its parent and
  {@link WatchEvent}s of the given kinds are filtered to concern the file
  in question. If the file is a directory then a {@link WatchService} is
  set up on the directory and all events are passed through of the given
  kinds.
  
  @param file
  file to watch
  @param kinds
  event kinds to watch for and emit
  @return observable of watch events