doc: add mscdex as collaborator

PR-URL: #972
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>

Author: mscdex

README.md

@@ -279,6 +279,7 @@ information about the governance of the io.js project, see
 * **Shigeki Ohtsu** ([@shigeki](https://github.com/shigeki)) <ohtsu@iij.ad.jp>
 * **Sam Roberts** ([@sam-github](https://github.com/sam-github)) <vieuxtech@gmail.com>
 * **Wyatt Preul** ([@geek](https://github.com/geek)) <wpreul@gmail.com>
+* **Brian White** ([@mscdex](https://github.com/mscdex)) <mscdex@mscdex.net>
 
 Collaborators follow the [COLLABORATOR_GUIDE.md](./COLLABORATOR_GUIDE.md) in
 maintaining the io.js project.