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

storyboard/ui.hpp

@@ -22,6 +22,7 @@ namespace storyboard {
     UI(const std::string& story_name);
 
     void init();
+    void update();
     void render(sf::RenderWindow &window);
     bool mouse(float x, float y, guecs::Modifiers mods);
     void zoom(const std::string &cell_name);