all: InterestHeader and ContentObjectHeader refactoring to Interest and ContentObject

refs #29
diff --git a/apps/ndn-consumer-zipf-mandelbrot.cc b/apps/ndn-consumer-zipf-mandelbrot.cc
index faebd6c..5d5d760 100644
--- a/apps/ndn-consumer-zipf-mandelbrot.cc
+++ b/apps/ndn-consumer-zipf-mandelbrot.cc
@@ -178,7 +178,7 @@
   (*nameWithSequence) (seq);
   //
 
-  InterestHeader interestHeader;
+  Interest interestHeader;
   interestHeader.SetNonce (m_rand.GetValue ());
   interestHeader.SetName  (nameWithSequence);