Apply Sentinel runtime configuration API introduced on Redis 2.8.4

* Implements new sentinel commands (failover, monitor, remove, set) 
* unit test included
** added 2 redis-server and 1 sentinel for failover test
* with some refactoring
** SentinelCommands : refactor to have interface
** HostAndPortUtil : same format to cluster setup

src/test/java/redis/clients/jedis/tests/utils/JedisSentinelTestUtil.java

@@ -46,8 +46,11 @@ public class JedisSentinelTestUtil {
 
 	    List<String> sentinelMasterInfos = sentinelJedis
 		    .sentinelGetMasterAddrByName(masterName);
-	    if (sentinelMasterInfos == null)
-		continue;
+	    if (sentinelMasterInfos == null) {
+	    	System.out
+		    .println("Cannot retrieve Sentinel's master address info, sleep...");
+	    	continue;
+	    }
 
 	    newMaster = new HostAndPort(sentinelMasterInfos.get(0),
 		    Integer.parseInt(sentinelMasterInfos.get(1)));