Robin Künzler

@briansmith : From our perspective it would be great if v3 certificates would be accepted regardless of whether they have extensions. AFAIU, the relevant code is [here](https://github.com/briansmith/webpki/blob/17d9189981a618120fd8217a913828e7418e2484/src/cert.rs#L104-L126). The der::nested currently...

@janimo : Thanks a lot, this looks good to me and it works for the certificates without extensions that I would like to use. Please see a more detailed comment...

@npmccallum : Would it be possible for you to release?