dashboard/app: add review subrepo, link changes correctly

Change-Id: I1eeea2beb4ffab690b2bb005c08a08d7e41c1fc3
Reviewed-on: https://go-review.googlesource.com/1503
Reviewed-by: Minux Ma <minux@golang.org>
Reviewed-by: Andrew Gerrand <adg@golang.org>