message: Add feature to return received msgs from nodes emulator.
diff: @@ -550,7 +550,7 @@ mod tests {
  use std::thread;
  use super::*;
  - pub fn start() -> (GenTransaction, thread::JoinHandle<()>) {
  + pub fn start() -> (GenTransaction, thread::JoinHandle<Vec<String>>) {
  let (pk, sk) = sodiumoxide::crypto::sign::ed25519::gen_keypair();
  let pkc = Ed25519ToCurve25519::crypto_sign_ed25519_pk_to_curve25519(&Vec::from(&pk.0 as &[u8]));
  let skc = Ed25519ToCurve25519::crypto_sign_ed25519_sk_to_curve25519(&Vec::from(&sk.0 as &[u8]));
  @@ -576,10 +576,13 @@ mod tests {
  s.set_curve_server(true).expect("set curve server");
  s.bind(addr.as_str()).expect("bind");
  let handle = thread::spawn(move || {
  + let mut received_msgs: Vec<String> = Vec::new();
  if s.poll(zmq::POLLIN, 100).expect("poll") == 1 {
  let v = s.recv_multipart(zmq::DONTWAIT).expect("recv mulp");
  s.send_multipart(&[v[0].as_slice(), "po".as_bytes()], zmq::DONTWAIT).expect("send mulp");
  + received_msgs.push(String::from_utf8(v[1].clone()).unwrap());
  }
  + received_msgs
  });
  (gt, handle)
  }
  