goprotobuf: add nigeltao to CONTRIBUTORS (Google CLA).
goprotobuf: add nigeltao to CONTRIBUTORS (Google CLA).

R=nigeltao, nigeltao_gnome
CC=golang-dev
http://codereview.appspot.com/4436065

jeremyletang/protobuf,jrbarron/protobuf,csuideal/protobuf,skyportsystems/go-protobuf,mwitkow-io/protobuf,aoeu/protobuf,hailocab/protobuf,fuchsia-mirror/third_party-github.com-golang-protobuf,daemonl/protobuf,tamird/protobuf-2,francoishill/protobuf,golang/protobuf,kung-foo/protobuf,trdata/protobuf,adnaan/protobuf,ekle/protoc-gen-goweb,trdata/protobuf,tamird/protobuf-2,alskjstl/protobuf,golang/protobuf,qinlodestar/protobuf,skyportsystems/go-protobuf,ekle/protoc-gen-goweb_test,jmptrader/protobuf-1,eduardiazf/protobuf,fuchsia-mirror/third_party-github.com-golang-protobuf,ArtemTeleshev/go-protobuf,velocity-toolkit/protobuf-1,linkedin-inc/protobuf