Update WSPingListener.java (#195)

Fix issue #155

Author: Vast-Nectarine

sdk/src/main/java/com/vk/api/sdk/streaming/clients/websocket/WSPingListener.java

@@ -25,6 +25,11 @@ public void onClose(WebSocket websocket, int code, String reason) {
         LOG.info("Close websocket" + websocket);
     }
 
+    @Override
+    public void onPingFrame(byte[] payload){
+        webSocket.sendPongFrame(payload);
+    }
+    
     @Override
     public void onError(Throwable t) {
         LOG.info("Websocket error " + t);