Contributors: add Kirklin McDonald (a Google employee)

R=gri
CC=golang-dev
https://golang.org/cl/1679045
diff --git a/CONTRIBUTORS b/CONTRIBUTORS
index f3bae98..68c5934 100644
--- a/CONTRIBUTORS
+++ b/CONTRIBUTORS
@@ -85,6 +85,7 @@
 Ken Friedenbach <kenliz@cruzio.com>
 Ken Thompson <ken@golang.org>
 Kevin Ballard <kevin@sb.org>
+Kirklin McDonald <kirklin.mcdonald@gmail.com>
 Kyle Consalus <consalus@gmail.com>
 Larry Hosken <lahosken@golang.org>
 Mark Zavislak <zavislak@google.com>