Add headers and events to serialization

- Relates to #35
- Now event headers and extended state variables
  are serialized with kryo and zookeeper.

spring-statemachine-core/src/main/java/org/springframework/statemachine/ensemble/StateMachinePersist.java

@@ -33,11 +33,11 @@ public interface StateMachinePersist<S, E, T> {
 	 * Write a {@link StateMachineContext} into a persistent store
 	 * with a context object {@code T}.
 	 *
-	 * @param contect the contect
+	 * @param context the context
 	 * @param contextOjb the context ojb
 	 * @throws Exception the exception
 	 */
-	void write(StateMachineContext<S, E> contect, T contextOjb) throws Exception;
+	void write(StateMachineContext<S, E> context, T contextOjb) throws Exception;
 
 	/**
 	 * Read a {@link StateMachineContext} from a persistent store

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

@@ -37,6 +37,15 @@ public class DefaultExtendedState implements ExtendedState {
 		this.variables = new HashMap<Object, Object>();
 	}
 
+	/**
+	 * Instantiates a new default extended state.
+	 *
+	 * @param variables the variables
+	 */
+	public DefaultExtendedState(Map<Object, Object> variables) {
+		this.variables = variables;
+	}
+
 	@Override
 	public Map<Object, Object> getVariables() {
 		return variables;