When selecting keys for encryption, don't select keys that have expired. Fixes golang/go#5808. R=bradfitz CC=golang-dev https://golang.org/cl/10847043
Fixes golang/go#2501. R=rsc, bradfitz CC=golang-dev https://golang.org/cl/5653067
Manual edits to README. Moved from main Go repository, deleted Makefiles, ran gofix -r go1rename. Tested with: go test code.google.com/p/go.crypto/... R=golang-dev, bradfitz CC=golang-dev https://golang.org/cl/5564059