go-tour: explain how to navigate The extant instructions mention the Next button, which doesn't exist, but not the table of contents menu, which does.
go-tour: explain how to navigate
The extant instructions mention the Next button, which doesn't exist,
but not the table of contents menu, which does.

R=adg
CC=golang-dev
https://codereview.appspot.com/13673043

BenjaminTsai/go-tour-zh-tw,BenjaminTsai/go-tour-zh-tw