initial integration of hyperplonk snark(#39)

transcript/src/lib.rs

@@ -87,8 +87,7 @@ impl<F: PrimeField> IOPTranscript<F> {
         let mut buf = [0u8; 64];
         self.transcript.challenge_bytes(label, &mut buf);
         let challenge = F::from_le_bytes_mod_order(&buf);
-        self.transcript
-            .append_message(label, &to_bytes!(&challenge)?);
+        self.append_serializable_element(label, &challenge)?;
         Ok(challenge)
     }