message: add SigningAlgorithm
diff: @@ -202,6 +202,7 @@ impl property::Deserialize for StakePoolRetirement {
  #[cfg(test)]
  mod test {
  use super::*;
  + use chain_crypto::SigningAlgorithm;
  use quickcheck::{Arbitrary, Gen};
  impl<T: Arbitrary, A: SigningAlgorithm> Arbitrary for Signed<T, A> {
  