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

R=golang-dev, dave, r
CC=golang-dev
http://codereview.appspot.com/6573065

h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang