doc: clarify that the displayed tar file name is an example

R=golang-dev, dave, r
CC=golang-dev
https://golang.org/cl/6573065

doc/install.html

@@ -116,13 +116,19 @@ rm -r /usr/local/go
 
 <p>
 Extract <a href="http://code.google.com/p/go/downloads/list?q=OpSys-FreeBSD+OR+OpSys-Linux+OR+OpSys-OSX+Type-Archive">the archive</a>
-into <code>/usr/local</code>, creating a Go tree in <code>/usr/local/go</code>:
+into <code>/usr/local</code>, creating a Go tree in <code>/usr/local/go</code>.
+For example:
 </p>
 
 <pre>
-tar -C /usr/local -xzf go1.0.2.linux-amd64.tar.gz
+tar -C /usr/local -xzf go1.0.3.linux-amd64.tar.gz
 </pre>
 
+<p>
+The name of the archive may differ, depending on the version of Go you are
+installing and your system's operating system and processor architecture.
+</p>
+
 <p>
 (Typically these commands must be run as root or through <code>sudo</code>.)
 </p>