misc/dashboard/codereview: add cshapiro and mpvl to reviewers list.
misc/dashboard/codereview: add cshapiro and mpvl to reviewers list.

R=golang-dev, gri
CC=golang-dev
https://codereview.appspot.com/9104052

h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang