Add an alternative to the swarm (#472)

* Rewrite the swarm

* Small improvement to Debug of ListenersStream

* Fix Swarm::Replaced never being produced

* Fix logic problem when reaching a node in swarm

* Small comment in swarm

* Add closed_multiaddr to Replaced event

* Add address to NodeClosed and NodeError

* Fix concerns

* Remove StreamMuxer::boxed

core/src/either.rs

@@ -210,6 +210,20 @@ where
             },
         }
     }
+
+    fn close_inbound(&self) {
+        match *self {
+            EitherOutput::First(ref inner) => inner.close_inbound(),
+            EitherOutput::Second(ref inner) => inner.close_inbound(),
+        }
+    }
+
+    fn close_outbound(&self) {
+        match *self {
+            EitherOutput::First(ref inner) => inner.close_outbound(),
+            EitherOutput::Second(ref inner) => inner.close_outbound(),
+        }
+    }
 }
 
 #[derive(Debug, Copy, Clone)]