To avoid ambiguity.

Mode is somewhat ambiguous term, which is often overused, for that reason I want to avoid it. This is a breaking change, but I don't guarantee stability yet, however I'll do my best to not break things.

Use a byte buffer for the password

Introduces a "UnicodeError" to express improperly encoded
passwords.

Move to stable

As this is a paththrough function and all important control chars
are in the byte range, chars is not necessary.