Fixups for upstream ed25519 crate changes

Author: tarcieri

tests/ed25519.rs

@@ -75,7 +75,7 @@ mod vectors {
 
 		    // The signatures in the test vectors also include the message
 		    // at the end, but we just want R and S.
-            let sig1: Signature = Signature::from_bytes(&sig_bytes[..64]).unwrap();
+            let sig1: Signature = Signature::try_from(&sig_bytes[..64]).unwrap();
             let sig2: Signature = keypair.sign(&msg_bytes);
 
             assert!(sig1 == sig2, "Signature bytes not equal on line {}", lineno);
@@ -102,7 +102,7 @@ mod vectors {
             PublicKey::from_bytes(&pub_bytes[..PUBLIC_KEY_LENGTH]).unwrap();
         let keypair: Keypair = Keypair::from(secret);
         assert_eq!(expected_public, keypair.public_key());
-        let sig1: Signature = Signature::from_bytes(&sig_bytes[..]).unwrap();
+        let sig1: Signature = Signature::try_from(&sig_bytes[..]).unwrap();
 
         let mut prehash_for_signing: Sha512 = Sha512::default();
         let mut prehash_for_verifying: Sha512 = Sha512::default();