CONTRIBUTORS: add Johnathan Pittman
CONTRIBUTORS: add Johnathan Pittman

(Google CLA)

R=rsc, bradfitz
CC=golang-dev
http://codereview.appspot.com/5544072

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