Write first round of unit tests

[phrohdoh]

Status	System under test	Relevant commit(s)
done	Kind::try_from_bytes	1b802c8
done	Archive::from_bytes	dd7f7e1, 83bfbde, 93fef5f
done	Archive::read_kind	83bfbde
done	Archive::read_size	bcbaa69
done	Archive::read_entry_metadata_table	19eaf98
done	Archive::get_bytes_via_table	b2733ec

[phrohdoh]

There is of course always more tests that can be written but for the time being I'm going to close this as the above functions have been tested.