The SwarmFuture is now a Stream (#442)

* The SwarmFuture is now a Stream

* Return the produced future in the message

* Remove IncomingConnection event

* Pass error when failing to dial

* Fix loop break mistake

* Fix concern

* Rename SwarmFuture to SwarmEvents

* Increase type length limit

* Remove todo

examples/echo-dialer.rs

@@ -133,6 +133,7 @@ fn main() {
     // actually started yet. Because we created the `TcpConfig` with tokio, we need to run the
     // future through the tokio core.
     let final_future = swarm_future
+        .for_each(|_| Ok(()))
         .select(finished_rx.map_err(|_| unreachable!()))
         .map(|_| ())
         .map_err(|(err, _)| err);