Camera is now using Animate2 and it's mostly working, but there's a few more refactors needed.

storyboard/ui.cpp

@@ -61,6 +61,10 @@ namespace storyboard {
     return sf::Time(out);
   }
 
+  void UI::update() {
+    $camera.update();
+  }
+
   void UI::track_audio() {
     auto& beat = $story.beats[cur_beat % $story.beats.size()];
     auto track_head = $audio->getPlayingOffset();