Support file removal and directory removal with polling

Conflicts:
	index.js
Fixed issue with multiple events fired on Windows
Use remove to throw unlink events
Improved check on file changed/delete

(cherry picked from commit 1675e3cdf133665c49767c1964707b2596425b93)
Use asynchronous exists

(cherry picked from commit ffeaddc1b3a0e45ba055aa95d8d83f4b2513e29d)

Conflicts:
	index.js
Existential condition