Added "keep" flag to songs, which will stop them being deleted.

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

@@ -95,6 +95,7 @@ public class MusicHandler implements AudioSendHandler, Closeable, Consumer<Song>
             }
             if (currentSong != null)
             {
+                if (!currentSong.isKept())
                     currentSong.delete();
                 currentSong = null;
             }

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

@@ -22,6 +22,7 @@ public class Song
 
     private String requestedBy;
     private String requestedIn;
+    private boolean kept = false;
 
     public Song(URL url)
     {
@@ -100,6 +101,16 @@ public class Song
         this.requestedIn = requestedIn;
     }
 
+    public boolean isKept()
+    {
+        return kept;
+    }
+
+    public void setKept(boolean kept)
+    {
+        this.kept = kept;
+    }
+
     @Override
     public String toString()
     {