Send acknowledgement message for new songs immediately, instead of after download is scheduled.

src/main/java/moe/nekojimi/chords/Chords.java

@@ -269,8 +269,8 @@ public final class Chords extends ListenerAdapter
         song.setNumber(trackNumber);
         trackNumber++;
         request.setSong(song);
-        downloader.accept(new Downloader.DownloadTask(request, queueManager));
         request.getInvocation().respond("Request pending...");
+        downloader.accept(new Downloader.DownloadTask(request, queueManager));
         return song;
     }