doc/effective_go.html: fix a couple of cosmetic issues
At the moment, godoc expands the example in the link, but in
the past it has not. Add a waffle word to allow either possibility.
Also change the order of cases in the switch in Compare to
be consistent with the other switch in the function.

R=golang-dev, iant
CC=golang-dev
https://codereview.appspot.com/14439055