v2.0.0 - Binary default

Don't base64 encode encrypted messages by default.

Breaking change:

• encrypt and encrypt-to do not encode its output as base64 per default anymore
• decrypt and decrypt-from do not expect its inputs base64 encoded per default anymore

Feature:

• encrypt, decrypt, encrypt-to and decrypt-from now take an optional parameter --base64 (or -b) to encode/decode message contents as base64