ae93e226e3 Remove hashes io feature (Tobin C. Harding)
Pull request description:
Currently we only get `std::io::Write` impls when the `bitcoin-io` dependency is used. This is overly restrictive, it would be nice to have `std::io::Write` imlps even without the `bitcoin-io` dependency.
Copy the logic out of the `bitcoin_io::impl_write` macro into `hashes` but feature gate it differently.
Call the new macro inside `hash_type` (and in `hmac`), remove the `impls` module, and move the tests to the integration test directory.
Remove the `io` feature from `hashes`, now if users enable `std` they get `std::io::Write` impls and if they enable `bitcoin-io` they get `bitcoin_io::Write` impls as well.
ACKs for top commit:
Kixunil:
ACK ae93e226e3
apoelstra:
ACK ae93e226e3 successfully ran local tests
Tree-SHA512: d47c9c060750e8a024c46cbf7afe8d0d1245fa1f5e575f36b3a11e2460d3620ad9def1a6331dafe77d46affc99b043ec9679e619ce8ddfa32436a5826ece09e4