doc: link to A Tour of Go

R=golang-dev, rsc, r
CC=golang-dev
https://golang.org/cl/5181045
diff --git a/doc/docs.html b/doc/docs.html
index c42116a..8b01e90 100644
--- a/doc/docs.html
+++ b/doc/docs.html
@@ -16,6 +16,16 @@
 idioms of programming in Go.
 </p>
 
+<h3 id="go_tour"><a href="http://go-tour.appspot.com/">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
+<a href="http://code.google.com/p/go-tour/">install it locally</a>.
+</p>
+
 <h3 id="orig_tutorial"><a href="go_tutorial.html">A Tutorial for the Go Programming Language</a></h3>
 <p>
 The first tutorial. An introductory text that touches upon several core