Support for kFSEventStreamCreateFlagNoDefer/low latency use cases

[kwasimensah]

Hi, I'm doing some profiling of my app and noticed it takes about 100ms for chokidar/fsevents to see that a directory is deleted.

I then dug through the code and saw the parameters passed to FSEventStreamCreate at https://github.com/fsevents/fsevents/blob/master/src/fsevents.c#L212 and saw the latency value of 0.1 and that kFSEventStreamCreateFlagNoDefer wasn't specified.

Can we make these configurable? FsEvents doesn't seem to currently take any configuration so I wasn't sure how you'd want to pipe these values through (especially since the goal is that this should come through chokidar).