Do not rebuild on extra Spotlight filesystem events

Do not rebuild on extra Spotlight filesystem events

Write and rename operations are often followed by CHMOD.
There may be valid use cases for rebuilding the site on CHMOD,
but that will require more complex logic than this simple conditional.

On OS X this seems to be related to Spotlight, see:
https://github.com/go-fsnotify/fsnotify/issues/15

A workaround is to put your site(s) on the Spotlight exception list,
but that may be a little mysterious for most end users.

So, for now, we skip reload on CHMOD.

This small commit will be a 100% improvement for most OS X-users.

Fixes #1587