Move register so it can be used by cryptography.hazmat.bindings.interfaces.
flesh out method definitions.
Change interface names to fit in the new smaller interface surface and
correct method names on interfaces.
Start documenting the backend interfaces.
de-opaque EVP_CIPHER_CTX a bit
Fix usages of interfaces.register
Document backend interfaces.
Merge pull request #267 from reaperhulk/evp-cipher-ctx-struct

de-opaque EVP_CIPHER_CTX a bit
modify nist loader to support multi-line GCM sections
Hashes and HMACs.
Move more uses of interfaces.register...
Move interfaces.register to utils.register_interface in preparation for more interface modules.
Merge pull request #270 from dreid/register-to-utils-register_interface

Move interfaces.register to utils.register_interface in preparation for more interface modules.
Merge branch 'master' into backend-interfaces
Merge branch 'master' into backend-interfaces
Some docstrings.
Describe what backends provide via these interfaces and that not all backends must provide all interfaces.
simplify nist loader to completely ignore sections
Merge pull request #268 from reaperhulk/nist-loader-section-fix

modify nist loader to support multi-line GCM sections
Merge pull request #269 from dreid/backend-interfaces

Backend interfaces