Version 2.3.1

Fixes a bug in the serialization of ED25519 keys to JWK (JSON), where X/D values ended up being switched for one another in the serialized output (see #224). Reading a serialized private key would also end up switching the X/D values for another, so keys that were serialized/deserialized with old versions of go-jose would work fine (values should end up in the correct place again). However, sharing a private key with another library would have caused problems. If you have private keys that were previously serialized to JWK using this library, the X/D values will be incorrect and will need to be switched in the JSON serialization before the key can be deserialized with an updated version of go-jose.