update to fxamacker/cbor v2 (#21)

Add implementations for txAuthSimple and txAuthGeneric extensions (#17)

prepare for v0.5 release (#16)

Add packed attestation verification (#12)

fido-u2f attestation verification (#11)

Finish reg (#7)

* Change `FinishRegistration` and `FinishAuthentication` functions to return more complete data
* Update interface method names to reduce the likelihood of implementing member conflicts
* Change most dealings of `CredentialID` to the raw form and allow the user to (un)marshal as needed

Fix appid implementation (#5)