a few more crypto tweaks
tcrypt.key can now use a custom hasher
adding HMAC authentication, as required by updates in issue #52. moving description parsing OUTSIDE of (de)serialization functions (makes sense), and adding/implementing defaults for cipher, block mode, padding, and KDF packages (0 index is no longer default). all encryption/decryption working beautifully, including old serialization function (albeit everything is a bit slower). also, added/implemented get_hasher helper.