add getDB() which return the db number we are connected to

src/test/java/redis/clients/jedis/tests/commands/AllKindOfValuesCommandsTest.java

@@ -343,6 +343,13 @@ public class AllKindOfValuesCommandsTest extends JedisCommandTestBase {
         assertArrayEquals(bbar, jedis.get(bfoo));
     }
 
+    @Test
+    public void getDB() {
+        assertEquals(0, jedis.getDB().longValue());
+        jedis.select(1);
+        assertEquals(1, jedis.getDB().longValue());
+    }
+
     @Test
     public void move() {
         long status = jedis.move("foo", 1);