CONTRIBUTORS: Add Jonathan Hseu (Google CLA)

Part of merging goprotobuf's A+C into Go's.

R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/6844096

CONTRIBUTORS

@@ -198,6 +198,7 @@ John Graham-Cumming <jgc@jgc.org> <jgrahamc@gmail.com>
 Jonathan Allie <jonallie@google.com>
 Jonathan Feinberg <feinberg@google.com>
 Jonathan Gold <jgold.bg@gmail.com>
+Jonathan Hseu <jhseu@google.com>
 Jonathan Mark <jhmark@xenops.com> <jhmark000@gmail.com>
 Jonathan Pittman <jmpittman@google.com> <jonathan.mark.pittman@gmail.com>
 Jonathan Wills <runningwild@gmail.com>