Add Roster.addSubscribeListener()

Remove unnecessary 'Unsubscribe' case in Roster: It is not required to
acknowledge these.

smack-integration-test/src/main/java/org/igniterealtime/smack/inttest/util/SimpleResultSyncPoint.java

@@ -0,0 +1,32 @@
+/**
+ *
+ * Copyright 2015 Florian Schmaus
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.igniterealtime.smack.inttest.util;
+
+public class SimpleResultSyncPoint extends ResultSyncPoint<Boolean, Exception> {
+
+    public void signal() {
+        signal(Boolean.TRUE);
+    }
+
+    public void signalFailure() {
+        signalFailure("Unspecified failure");
+    }
+
+    public void signalFailure(String failureMessage) {
+        signal(new Exception(failureMessage));
+    }
+}