go-tour: link to screencast from final page of tour
go-tour: link to screencast from final page of tour

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/6852043

bbandaru/tour,shuLhan/go-tour-id,raindev/tour,golang/tour,Jasperste/tour,LaPingvino/go-tour-nl,LaPingvino/go-tour-nl,scryner/tour,Go-zh/tour,Go-zh/tour,raindev/tour,LaPingvino/go-tour-eo,phoorichet/tour,raindev/tour,scryner/tour,Go-zh/tour,phoorichet/tour,shuLhan/tour,campoy/go-tour-ua,shuLhan/tour,bbandaru/tour,tamnd/tour,Jasperste/tour,dupoxy/go-tour-fr,phoorichet/tour,ybin/tour,shuLhan/go-tour-id,tamnd/tour,Go-zh/tour,rofrol/go-tour-pl,scryner/tour,shuLhan/go-tour-id,Jasperste/tour,tamnd/tour,dupoxy/go-tour-fr,campoy/go-tour-ua,ybin/tour,shuLhan/tour,scryner/tour,campoy/go-tour-ua,golians/tour,LaPingvino/go-tour-nl,LaPingvino/go-tour-eo,LaPingvino/go-tour-eo,ybin/tour,golians/tour,rofrol/go-tour-pl,golians/tour,zorion/go-tour-ca,zorion/go-tour-ca,rofrol/go-tour-pl,bbandaru/tour,dupoxy/go-tour-fr