doc: refer to tour.golang.org instead of go-tour.appspot.com

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5331055

doc/docs.html

@@ -16,13 +16,13 @@ Once you've learned a little about the language,
 idioms of programming in Go.
 </p>
 
-<h3 id="go_tour"><a href="http://go-tour.appspot.com/">A Tour of Go</a></h3>
+<h3 id="go_tour"><a href="http://tour.golang.org/">A Tour of Go</a></h3>
 <p>
 An interactive introduction to Go in three sections.
 The first section covers basic syntax and data structures; the second discusses
 methods and interfaces; and the third introduces Go's concurrency primitives.
 Each section concludes with a few exercises so you can practice what you've
-learned. You can <a href="http://go-tour.appspot.com/">take the tour online</a> or
+learned. You can <a href="http://tour.golang.org/">take the tour online</a> or
 <a href="http://code.google.com/p/go-tour/">install it locally</a>.
 </p>
 

doc/root.html

@@ -51,7 +51,7 @@ google.setOnLoadCallback(loadFeed);
       </p>
       <h2>
         Get started now with
-	<a target="_blank" href="http://go-tour.appspot.com/">A Tour of Go</a>
+	<a target="_blank" href="http://tour.golang.org/">A Tour of Go</a>
         in your browser.
       </h2>
       <p>