message: [cli] improve output of wait_for_transaction
  few output changes:
  * `waiting` instead of `[waiting`
  * `no events emitted` is displayed in case of absence of events
diff: @@ -300,7 +300,7 @@ impl ClientProxy {
  /// Waits for the next transaction for a specific address and prints it
  pub fn wait_for_transaction(&mut self, account: AccountAddress, sequence_number: u64) {
  let mut max_iterations = 5000;
  - print!("[waiting ");
  + print!("waiting ");
  loop {
  stdout().flush().unwrap();
  max_iterations -= 1;
  @@ -311,7 +311,7 @@ impl ClientProxy {
  {
  println!("transaction is stored!");
  if events.is_empty() {
  - println!("but it didn't emit any events");
  + println!("no events emitted");
  }
  break;
  } else if max_iterations == 0 {
  