This adds examples showing the different ways of using sort.Search.

Change-Id: Iaa08b4501691f37908317fdcf2e618fbe9f99ade
Reviewed-on: https://go-review.googlesource.com/29131Reviewed-by: Andrew Gerrand <adg@golang.org>
Run-TryBot: Andrew Gerrand <adg@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>