Modified RSA algorithms to use cryptography library instead of PyCrypto
Modified ECDSA algorithms to use cryptography library instead of ecdsa.
Added some missing ensure_bytes in a couple of the tests.
Consolidated testing variables for has_rsa and has_ecdsa into has_crypto.
Updated README and dependencies in tox.ini
Added name to AUTHORS
Incremented version to 0.4
Merge pull request #51 from mark-adams/change-to-cryptography

Switch to cryptography for RSA and ECDSA algorithms