Adds back displaying the currently playing song as such in the queue

We no longer alter the song, the queue gets this from the player.
That way we can't have two songs marked as 'playing' at the same time.

app/queue/queue_test.js

@@ -2,9 +2,7 @@ describe("Queue controller", function() {
     'use strict';
 
     var player, scope, globals;
-    var song = {
-        id: 7310
-    };
+    var song;
 
     beforeEach(function() {
         module('jamstash.queue.controller');
@@ -20,6 +18,7 @@ describe("Queue controller", function() {
                 player: player
             });
         });
+        song = { id: 7310 };
     });
 
     it("When I play a song, it calls play in the player service", function() {
@@ -59,4 +58,10 @@ describe("Queue controller", function() {
         scope.removeSelectedSongsFromQueue();
         expect(player.removeSongs).toHaveBeenCalledWith([song, secondSong]);
     });
+
+    it("asks the player service if a given song is the currently playing song", function() {
+        spyOn(player, "getPlayingSong").and.returnValue(song);
+        expect(scope.isPlayingSong(song)).toBeTruthy();
+        expect(player.getPlayingSong).toHaveBeenCalled();
+    });
 });