message: remove HasTransaction from the block
  this trait has been remove from the core api
diff: @@ -174,26 +174,6 @@ impl property::Deserialize for Block {
  }
  }
  -impl property::HasTransaction for Block {
  - type Transaction = SignedTransaction<Address>;
  - fn transactions<'a>(&'a self) -> Box<Iterator<Item = &SignedTransaction<Address>> + 'a> {
  - Box::new(self.contents.0.iter().filter_map(|msg| match msg {
  - Message::Transaction(tx) => Some(tx),
  - _ => None,
  - }))
  - }
  -
  - fn for_each_transaction<F>(&self, mut f: F)
  - where
  - F: FnMut(&Self::Transaction),
  - {
  - self.contents.0.iter().for_each(|msg| match msg {
  - Message::Transaction(tx) => f(tx),
  - _ => {}
  - })
  - }
  -}
  -
  impl property::HasMessages for Block {
  type Message = Message;
  fn messages<'a>(&'a self) -> Box<Iterator<Item = &Message> + 'a> {
  