Fix wrong event object comparison

- Classic case of using == vs. equals if Strings are involved.
- In DefaultStateMachineExecutor change event comparison
  from == to equals.
- Tests using enums naturally work, but some tests using Strings
  had a wrong checks.
- Fixes #253

spring-statemachine-core/src/main/java/org/springframework/statemachine/support/DefaultStateMachineExecutor.java

@@ -366,8 +366,8 @@ public class DefaultStateMachineExecutor<S, E> extends LifecycleObjectSupport im
 						Trigger<S, E> tri = e.getKey();
 						E ee = tri.getEvent();
 						Transition<S, E> tra = e.getValue();
-						if (event == ee) {
-							if (tra.getSource().getId() == id && !trans.contains(tra)) {
+						if (event.equals(ee)) {
+							if (tra.getSource().getId().equals(id) && !trans.contains(tra)) {
 								trans.add(tra);
 								continue;
 							}