Log Message:
Update ruby-yard to 0.9.9.

Release v0.9.9				2017/04/23

* Added gem uninstall hooks to remove YARD documentation files. (#1083)
* Added support for C++ namespaces. (#809)
* Fixed issue where loading a .html page via an anchor would not scroll to
  the anchor section. (#1082)
* Hide some Ruby warnings.
* Improve progress indicator icons in terminal.