Add self to CONTRIBUTORS.txt

See #3958.

CONTRIBUTORS.txt

@@ -233,3 +233,4 @@ Morgan Doocy, 2017/01/02
 Arcadiy Ivanov, 2017/01/08
 Ryan Hiebert, 2017/01/20
 Jianjian Yu, 2017/04/09
+Brian May, 2017/04/10