Add simple stateChanges map into Simulation

lib/src/Engine.dart

@@ -101,7 +101,8 @@ class Engine {
   /// directly, since it is automatically taken care of by the processing function.
   /// If simulation should be advanced manually one time, prefer using step().
   void update() {
-    if (!_grid.update()) running = false;
+    // TODO: create hasUpdated/hasAdvanced method in simulation to abstract actual updating away
+    if (_grid.update().length != 0) running = false;
   }
 
   /// Advances Logic One Update