message: remove non necessary use of unwrap
  here it is safer to use `util::hex::encode`
  relates to
diff: @@ -7,10 +7,10 @@ use cryptoxide::blake2b::Blake2b;
  use cryptoxide::sha3::Sha3;
  use redeem;
  -use util::{base58};
  +use util::{base58, hex};
  use cbor;
  use cbor_event::{self, de::RawCbor, se::{Serializer}};
  -use hdwallet::{XPub};
  +use hdwallet::{self, XPub};
  use hdpayload::{HDAddressPayload};
  /// Digest of the composition of `Blake2b_224 . Sha3_256`
  @@ -45,14 +45,7 @@ impl DigestBlake2b224 {
  }
  impl fmt::Display for DigestBlake2b224 {
  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
  - self.0.iter().for_each(|byte| {
  - if byte < &0x10 {
  - write!(f, "0{:x}", byte).unwrap()
  - } else {
  - write!(f, "{:x}", byte).unwrap()
  - }
  - });
  - Ok(())
  + write!(f, "{}", hex::encode(&self.0))
  }
  }
  impl cbor_event::se::Serialize for DigestBlake2b224 {
  