Mark as experimental, guide users to golang.org/x/crypto/ed25519

[tv42]

Hi. I just stumbled on a project still importing this. As far as I understand, this code has long since migrated to https://godoc.org/golang.org/x/crypto/ed25519 and this repo may perhaps be used for future experiments (<- #18 (comment) ).

However, this repo still keeps coming up in searches, e.g. https://godoc.org/?q=ed25519 and nothing guides people to the more stable variant. To minimize confusion and likelihood of people picking the wrong one, it would probably be best to neuter this repo somehow. As an outsider, this issue showing up should at least nudge people in the right direction. Hopefully you'll have to time to do something a bit more.

Thanks for all your work!

[OwenJacob]

The golang package is missing the ed25519 to curve25519 key conversion code so please don't depreciate this repo :)

AFAIK this is the only native Go code for converting between keys

[baha-ai]

The golang package is missing the ed25519 to curve25519 key conversion code so please don't depreciate this repo :)

AFAIK this is the only native Go code for converting between keys

@OwenJacob use "github.com/teserakt-io/golang-ed25519/extra25519" instead... seems to work just fine.