CHANGED Listener.newBlock is a shared observable

CHANGED version to 0.9.4

Author: Aleix Morgadas

package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "nem2-sdk",
-  "version": "0.9.3",
+  "version": "0.9.4",
   "description": "Reactive Nem2 sdk for typescript and javascript",
   "scripts": {
     "pretest": "npm run build",

package.json

@@ -16,6 +16,7 @@
 
 import 'rxjs/add/operator/filter';
 import 'rxjs/add/operator/map';
+import 'rxjs/add/operator/share';
 import {Observable} from 'rxjs/Observable';
 import {Subject} from 'rxjs/Subject';
 import * as WebSocket from 'ws';
@@ -186,7 +187,9 @@ export class Listener {
      */
     public newBlock(): Observable<BlockInfo> {
         this.subscribeTo('block');
-        return this.messageSubject.asObservable()
+        return this.messageSubject
+            .asObservable()
+            .share()
             .filter((_) => _.channelName === ListenerChannelName.block)
             .filter((_) => _.message instanceof BlockInfo)
             .map((_) => _.message as BlockInfo);