message: expose the Signing Algorithm
diff: @@ -14,6 +14,6 @@ mod key;
  mod sign;
  pub use key::{AsymmetricKey, PublicKey, PublicKeyError, SecretKey, SecretKeyError};
  -pub use sign::Signature;
  +pub use sign::{Signature, SignatureError, SigningAlgorithm, Verification};
  pub use algorithms::*;
  