x/tools/godoc/redirect: add redirect for Gerrit reviews at /review/
x/tools/godoc/redirect: add redirect for Gerrit reviews at /review/

LGTM=rsc, bradfitz
R=bradfitz, rsc
CC=golang-codereviews
https://codereview.appspot.com/178960043

karmakaze/go.tools,karmakaze/go.tools,karmakaze/go.tools,karmakaze/go.tools,karmakaze/go.tools