The cornerstone API is a more memory-efficient Unmarshal.
The savings come from re-using a json.Decoder.
BenchmarkUnmarshal-8 4016418 288 ns/op 8 B/op 1 allocs/op
BenchmarkStdUnmarshal-8 4189261 283 ns/op 184 B/op 2 allocs/op
It also includes a Bytes type to reduce allocations
when unmarshalling a non-hex-encoded JSON string into a []byte.
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
