Sebastian Hahn

I had some questions in https://github.com/briansmith/webpki/pull/87#discussion_r279227530 that probably got overlooked. I'll try to find some time to rebase it and see if I can come up with answers to some...

I wanted to pick this back up, but there's one catch with the idea of pre-parsing the SPKI. It would be a change of public API of `TrustAnchor` to store...