message: Verify that the volume starts at 1.0
diff: @@ -124,6 +124,7 @@ fn volume_persists_after_play() {
  {
  let volume = 0.8;
  let mut sound = audio::Source::new(c, filename).unwrap();
  + assert_eq!(sound.volume(), 1.0);
  sound.set_volume(volume);
  assert_eq!(sound.volume(), volume);
  sound.play().unwrap();
  @@ -133,6 +134,7 @@ fn volume_persists_after_play() {
  {
  let volume = 0.8;
  let mut sound = audio::SpatialSource::new(c, filename).unwrap();
  + assert_eq!(sound.volume(), 1.0);
  sound.set_volume(volume);
  assert_eq!(sound.volume(), volume);
  sound.play().unwrap();
  