model: Enabling serialization/deserialization of Exclude filter in ndnSIM wire format

Refs #1009 (http://redmine.named-data.net/issues/1009)
diff --git a/ndn.cxx/exclude.h b/ndn.cxx/exclude.h
index 70b8f54..8315f34 100644
--- a/ndn.cxx/exclude.h
+++ b/ndn.cxx/exclude.h
@@ -11,8 +11,9 @@
 #ifndef NDN_EXCLUDE_H
 #define NDN_EXCLUDE_H
 
-#include "name-component.h"
+#include <ns3/simple-ref-count.h>
 
+#include "name-component.h"
 #include <map>
 
 NDN_NAMESPACE_BEGIN
@@ -20,7 +21,7 @@
 /**
  * @brief Class to represent Exclude component in NDN interests
  */
-class Exclude
+class Exclude : public SimpleRefCount<Exclude>
 {
 public:
   typedef std::map< name::Component, bool /*any*/, std::greater<name::Component> > exclude_type;
@@ -35,6 +36,8 @@
    */
   Exclude ();
 
+  // no need for explicit copy constructor
+
   /**
    * @brief Check if name component is excluded
    * @param comp Name component to check against exclude filter