CONTRIBUTORS: add James Robinson (Google CLA)

LGTM=iant
R=golang-codereviews, iant
CC=dvyukov, golang-codereviews, jamesr, nigeltao
https://golang.org/cl/155530043

CONTRIBUTORS

@@ -281,6 +281,7 @@ James Fysh <james.fysh@gmail.com>
 James Gray <james@james4k.com>
 James Meneghello <rawrz0r@gmail.com>
 James P. Cooper <jamespcooper@gmail.com>
+James Robinson <jamesr@google.com> <jamesr.gatech@gmail.com>
 James Toy <nil@opensesame.st>
 James Tucker <raggi@google.com>
 James Whitehead <jnwhiteh@gmail.com>