go-tour: use tabs for indentation

LGTM=adg
R=adg, kevlar
CC=golang-codereviews
https://codereview.appspot.com/145160043
go-tour: fix typo in comment

LGTM=adg
R=adg, kevlar
CC=golang-codereviews
https://codereview.appspot.com/143310043
go-tour: add semicolons removed accidnetally by gofmt

LGTM=adg
R=adg
CC=golang-codereviews
https://codereview.appspot.com/148990046
Merge branch 'master' of hg::https://code.google.com/p/go-tour