Invoke (Before|After)Class and TestRules around Cucumber execution

Junit invokes several framework methods around the test execution.
The cucumber runner should finish its whole execution inside these.

To be precises these two should be equivalent:

```
@BeforeClass
public static void before {
   // Do stuff
}

@test
public void test(){
    cucumber.api.cli.Main.main(some arguments....)
}

@afterclass
public static void after {
   // Do stuff
}

```

```
@RunWith(Cucumber.class)
public class Test {
    @BeforeClass
    public static void before {
       // Do stuff
    }

    @afterclass
    public static void after {
     // Do stuff
    }
}
```

By firing the TestRunFinished event and printing the summary directly
after invoking the children rather then after the completion of the
whole test run these are made equivalent again.

Author: mpkorstanje

junit/src/main/java/cucumber/api/junit/Cucumber.java

@@ -19,6 +19,7 @@
 import org.junit.runner.notification.RunNotifier;
 import org.junit.runners.ParentRunner;
 import org.junit.runners.model.InitializationError;
+import org.junit.runners.model.Statement;
 
 import java.io.IOException;
 import java.util.ArrayList;
@@ -75,7 +76,7 @@ public Cucumber(Class clazz) throws InitializationError, IOException {
      * @param runtimeOptions configuration
      * @return a new runtime
      * @throws InitializationError if a JUnit error occurred
-     * @throws IOException if a class or resource could not be loaded
+     * @throws IOException         if a class or resource could not be loaded
      */
     protected Runtime createRuntime(ResourceLoader resourceLoader, ClassLoader classLoader,
                                     RuntimeOptions runtimeOptions) throws InitializationError, IOException {
@@ -99,10 +100,16 @@ protected void runChild(FeatureRunner child, RunNotifier notifier) {
     }
 
     @Override
-    public void run(RunNotifier notifier) {
-        super.run(notifier);
-        runtime.getEventBus().send(new TestRunFinished(runtime.getEventBus().getTime()));
-        runtime.printSummary();
+    protected Statement childrenInvoker(RunNotifier notifier) {
+        final Statement features = super.childrenInvoker(notifier);
+        return new Statement() {
+            @Override
+            public void evaluate() throws Throwable {
+                features.evaluate();
+                runtime.getEventBus().send(new TestRunFinished(runtime.getEventBus().getTime()));
+                runtime.printSummary();
+            }
+        };
     }
 
     private void addChildren(List<CucumberFeature> cucumberFeatures) throws InitializationError {