all: Adding typedefs near forward declarations of Interest/ContentObject/Name

refs #29
diff --git a/helper/ndn-header-helper.h b/helper/ndn-header-helper.h
index cce07dd..c8c46c9 100644
--- a/helper/ndn-header-helper.h
+++ b/helper/ndn-header-helper.h
@@ -31,6 +31,7 @@
 namespace ndn {
 
 class Name;
+typedef Name NameComponents;
 
 /**
  * \ingroup ndn-helpers