CONTRIBUTORS: added Paul Chang (Google CLA)

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/6569078

CONTRIBUTORS

@@ -268,6 +268,7 @@ Patrick Gavlin <pgavlin@gmail.com>
 Patrick Higgins <patrick.allen.higgins@gmail.com>
 Patrick Mylund Nielsen <patrick@patrickmn.com>
 Paul Borman <borman@google.com>
+Paul Chang <paulchang@google.com>
 Paul Lalonde <paul.a.lalonde@gmail.com>
 Paul Sbarra <Sbarra.Paul@gmail.com>
 Petar Maymounkov <petarm@gmail.com>