size method added to ClusterSlotRange

src/main/java/org/redisson/cluster/ClusterSlotRange.java

@@ -1,5 +1,5 @@
 /**
- * Copyright 2016 Nikita Koksharov
+ * Copyright 2014 Nikita Koksharov, Nickolay Borbit
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -34,6 +34,10 @@ public class ClusterSlotRange {
         return endSlot;
     }
     
+    public int size() {
+        return endSlot - startSlot + 1;
+    }
+
     public boolean isOwn(int slot) {
         return slot >= startSlot && slot <= endSlot;
     }