Fix single steps not updating simulation

lib/src/Engine.dart

@@ -101,7 +101,6 @@ 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() {
-    // TODO: create hasUpdated/hasAdvanced method in simulation to abstract actual updating away
     Map<int, bool> simulationUpdate = _simulation.update();
     _simulation.mergeStateChanges(simulationUpdate);
 
@@ -114,8 +113,8 @@ class Engine {
   /// simulation. Does not automatically re-render the new state
   /// (though this should usually not pose a problem).
   void step() {
+    update();
     running = false;
-    _simulation.update();
   }
 
   /// Renders the Current Simulation State