Add support for ACME TLS Certificates

[aeneasr]

https://godoc.org/golang.org/x/crypto/acme/autocert

[aeneasr]

I've looked into this and it doesn't make sense for a couple of reasons:

1. Lets's Encrypt only works with registered domains, it will not work with localhost or custom domains routed via /etc/hosts. It thus doesn't work in development which would have been the only logical use case, because:
2. Maintaining certificates for public URLs should not be in the domain of this project but instead of something like e.g. certbot.