Cert file hashing#3

Open

greimers wants to merge 3 commits intonicwise:masterfrom

greimers:cert-file-hashing

Commits on Feb 24, 2017

- get public key data from SecKey without KeyChain on iOS 10+
greimers
committed
- added hashForDERCertificate function to calculate hashes offline from DER files
greimers
committed
added instructions to hash local certificate file to readme
greimers
committed