go-playground: add rich snippet.
go-playground: add rich snippet.

R=adg, bradfitz, rsc
CC=golang-dev
http://codereview.appspot.com/6171044

Committer: Andrew Gerrand <395a7d33bec8475c9b83b7d440f141bcbd994aa5@golang.org>

stevelacy/go-playground,Alexandr-Penkin/go-playground,Alexandr-Penkin/go-playground,stevelacy/go-playground