Changes since version 0.10.14:

* fsevents: create FSEvents thread on demand (Ben Noordhuis)

* fsevents: use a single thread for interacting with FSEvents, because it's not
  thread-safe. (Fedor Indutny)

* fsevents: share FSEventStream between multiple FS watchers, which removes a
  limit on the maximum number of file watchers that can be created on OS X.
  (Fedor Indutny)