Gem-ize jasmine

[Finishes #13128217]

lib/jasmine-core/example/spec/SpecHelper.js

@@ -0,0 +1,9 @@
+beforeEach(function() {
+  this.addMatchers({
+    toBePlaying: function(expectedSong) {
+      var player = this.actual;
+      return player.currentlyPlayingSong === expectedSong && 
+             player.isPlaying;
+    }
+  });
+});