Package autocert provides automatic access to certificates
from Let's Encrypt and any other ACME-based CA.
It is heavily based on the ideas from rsc.io/letsencrypt.
Change-Id: I62021452a918cd49093162f3d6c74e9d7f452fb8
Reviewed-on: https://go-review.googlesource.com/23970
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
