godoc: move Examples above Index and make them both collapsable
godoc: move Examples above Index and make them both collapsable

R=golang-dev, dsymonds, bradfitz, r
CC=golang-dev
http://codereview.appspot.com/6591066
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go