implement Cipher PEP 272 API for Block Encryption Algorithms

[clach04]

Cipher PEP 272 API for Block Encryption Algorithms v1.0 https://www.python.org/dev/peps/pep-0272/

See https://github.com/clach04/openssl_enc_compat/blob/5445492c639c2d0dd566b2d3c0ac5b131c50b792/openssl_enc_compat/cipher.py#L87