encoding: Adding missing include

Change-Id: Ib7de4d7112eb3f8104449c5a71a63275a82cafda
Refs: #1864
diff --git a/src/encoding/tlv.hpp b/src/encoding/tlv.hpp
index 87114eb..ecd9453 100644
--- a/src/encoding/tlv.hpp
+++ b/src/encoding/tlv.hpp
@@ -23,7 +23,9 @@
 #define NDN_ENCODING_TLV_HPP
 
 #include <stdexcept>
+#include <iostream>
 #include <iterator>
+
 #include "buffer.hpp"
 #include "endian.hpp"