[x/tour] go-tour: add Catalan translation
[x/tour] go-tour: add Catalan translation

R=golang-dev, r, bradfitz
CC=golang-dev
https://golang.org/cl/7314094
X-Tour-Commit: 4fa06497f72b19239ebfc316d04f1fa27a62f5c2

golang/website,golang/website,golang/website,golang/website,golang/website,golang/website,golang/website