Progress: Further work in TacocaT.

Progress: Further work in TacocaT.

The payload is now the only thing that gets written.

The next things to do are to:
- Process the headers and possibly the signatures.
- Go through a lot of the error cases and make sure they are handled.
- Address all of the todo and fixme comments.
- Consider supporting encryption and including optional third-party libraries to perform such tasks.