doc: make it point to correct go1.3.1 change history
doc: make it point to correct go1.3.1 change history

LGTM=minux, adg
R=golang-codereviews, minux, adg
CC=golang-codereviews
https://codereview.appspot.com/129180043

tv42/old-go,tv42/old-go,tv42/old-go,tv42/old-go,tv42/old-go,tv42/old-go,tv42/old-go