Log Message:
Update ruby-rb-kqueue to 0.2.5.

0.2.5 (2017/05/16)

* Use types in agreement with the event.h of native operating systems.
* Use EVFILT_ flags in agreement with the event.h of native operating systems.
* Add RSpec development dependency.
* Generate initial RSpec config.
* [WIP] Write basic tests for KQueue::Queue#watch_file.