morning brings wisdom: performance improvement by removing the finalizer

once it is no longer needed.

install finalizers for the reader and Writer structs

so that if, for some reason, the calling code fails to Close() the
reader or Writer, we do not leak the z.zstrm's C malloc allocations.

Note that it is safe to call (*reader).Close() and (*Writer).Close()
multiple times: they both set z.err to io.EOF, which then causes
the later calls to short circuit.

Remove `TestEofAndData` since it adds a lot of dependencies

that we dont really care for; and we dont care about this test

goimports -w my change

Record the exact version of what was benchmarked