doc/go1.3.html: add note about small map iteration order
doc/go1.3.html: add note about small map iteration order

LGTM=r
R=r
CC=golang-codereviews
https://codereview.appspot.com/98290048

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