add PKCS8SerializationBackend support to MultiBackend
change some nomenclature
remove unneeded try/catch
Merge pull request #1222 from reaperhulk/add-pkcs8serialization-multibackend

add PKCS8SerializationBackend support to MultiBackend
0.5.1 version bump
Merge pull request #1226 from reaperhulk/lets-do-051

0.5.1 version bump
open master for development on the sixth release
Merge pull request #1227 from reaperhulk/open-for-business

open master for development on the sixth release
Remove merge leftovers
Merge pull request #1228 from Ayrx/remove-merge-leftovers

Remove merge leftovers