mix raxol.rate (Raxol v2.6.1)

Render the fixture corpus and compare each hash against priv/rate/golden.refs.

$ mix raxol.rate          # compare, exit non-zero on any mismatch
$ mix raxol.rate --gen    # regenerate the references

Hashes are architecture-independent; a mismatch on one arch and not another points at a real render determinism bug.