re-add CAST5 ECB support (OpenSSL & CC backends). fixes #417
add cbc, cfb, ofb support to CAST5 (aka CAST128) for openssl & cc

fixes #393
add cast5 docs
remove some extra linebreaks
Merge pull request #604 from reaperhulk/cast5-cbc-and-more

CAST5 Support (ECB, CBC, CFB, OFB)