Update to use renderer accessor.

src/level.cxx

@@ -140,12 +140,12 @@ void level::update_waves(float delta) {
 }
 
 void level::render() {
-  renderer->draw(player_->render_info());
+  renderer().draw(player_->render_info());
   for (auto & a : actors_) {
-    renderer->draw(a->render_info());
+    renderer().draw(a->render_info());
   }
   for (auto & b : bullets_) {
-    renderer->draw(b->render_info());
+    renderer().draw(b->render_info());
   }
-  renderer->flush();
+  renderer().flush();
 }