tour: Updated readme to specify commands needed for newbies.

Added the path to where this package was installed and the command to start the web server.
It was not intuitive to me and I thought this might help others.

Change-Id: Ifbc850d5ad909b5bdf6e3a4b28b14dfad2727786
Reviewed-on: https://go-review.googlesource.com/14920
Reviewed-by: Andrew Gerrand <adg@golang.org>
diff --git a/README b/README
index b28974b..001e825 100644
--- a/README
+++ b/README
@@ -3,6 +3,8 @@
 To install the tour locally, first install Go, then run:
 
 	$ go get golang.org/x/tour/gotour
+	$ cd $GOPATH/bin
+	$ ./gotour
 
 Unless otherwise noted, the go-tour source files are distributed
 under the BSD-style license found in the LICENSE file.