encoding: remove duplicate buf() and get() methods from Buffer class

Change-Id: If885d4199d6c9df9b9b46664c3641c9a14a77eab
diff --git a/tools/ndnsec/sign-req.cpp b/tools/ndnsec/sign-req.cpp
index da330cf..a03a595 100644
--- a/tools/ndnsec/sign-req.cpp
+++ b/tools/ndnsec/sign-req.cpp
@@ -1,5 +1,5 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/**
+/*
  * Copyright (c) 2013-2017 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
@@ -99,7 +99,7 @@
   certificate.setFreshnessPeriod(time::hours(1));
 
   // set content
-  certificate.setContent(key.getPublicKey().buf(), key.getPublicKey().size());
+  certificate.setContent(key.getPublicKey().data(), key.getPublicKey().size());
 
   // set signature-info
   SignatureInfo signatureInfo;