Currently in order to release `hashes v1.0` we need to 1.0 `io` as well.
For multiple reasons, many out of our control, the `io` crate may not
stabalise any time soon.
Instead we can invert the dependency between the two crates.
This is an ingenious idea, props to Kixunil for coming up with it.
Notes
- `io` does not currently re-export the `hashes` crate.
- This work highlights that we cannot call `hash_reader` on a siphash.
- The `Hmac::hash_reader` uses the default key which may not be obvious.
Signed-off-by: Tobin C. Harding <me@tobin.cc>
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