fix(watch hidden key) Fix hidden keys preventing deeper recursive watches from receiving events
If a watcher has given the correct hidden directory, we should allow it to watch the non-hidden events under that hidden directory. This pull request achieves this by checking if the path after the watching prefix has a "/_" which indicates a hidden key.
chrod(watcher_hub) add comment to isHidden function
test (isHidden) add unit test for isHidden function
Merge pull request #537 from xiangli-cmu/fix_hidden_watch

fix(watch hidden key)