doc: add a couple net/http go1.3 items
doc: add a couple net/http go1.3 items

LGTM=r
R=r
CC=golang-codereviews
https://codereview.appspot.com/85760043

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