* Added raw_sign() and raw_sign_prehashed() functions
* Renamed `nonce` to `hash_prefix` in signing because it's really not a nonce
* Moved raw signing to hazmat module
* impl From<EdwardsPoint> for VerifyingKey
* Brought back ExpandedSecretKey; made raw_* functions take it as input
* Added remaining features to docs.rs feature set
* Removed redundant ExpandedSecretKey def; made raw signing use a generic CtxDigest
* Implemented raw_verify with generic CtxDigest
* Implemented raw_verify_prehashed with generic MsgDigest and CtxDigest
* Wrote hazmat tests; fixed errors; switched ordering of MsgDigest and CtxDigest
* Updated changelog
* ExpandedSecretKey::from_bytes takes an array and is now infallible
* Add TODO comment for split_array_ref
* Added from_slice and TryFrom<&[u8]> for ExpandedSecretKey
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Co-authored-by: Tony Arcieri <bascule@gmail.com>
