doc: add yosuke-furukawa as collaborator

PR-URL: https://github.com/iojs/io.js/pull/1183
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Rod Vagg <rod@vagg.org>
Reviewed-By: Shigeki Ohtsu <ohtsu@iij.ad.jp>

README.md

@@ -286,6 +286,7 @@ information about the governance of the io.js project, see
 * **Johan Bergström** ([@jbergstroem](https://github.com/jbergstroem)) <bugs@bergstroem.nu>
 * **Roman Reiss** ([@silverwind](https://github.com/silverwind)) <me@silverwind.io>
 * **Petka Antonov** ([@petkaantonov](https://github.com/petkaanotnov)) <petka_antonov@hotmail.com>
+* **Yosuke Furukawa** ([@yosuke-furukawa](https://github.com/yosuke-furukawa)) <yosuke.furukawa@gmail.com>
 
 Collaborators follow the [COLLABORATOR_GUIDE.md](./COLLABORATOR_GUIDE.md) in
 maintaining the io.js project.