docs: Correct copyright statements

Change-Id: Ie1a5a88a411e7d3893abeb5a810dff28ae3256b5
diff --git a/src/util/signal-connection.cpp b/src/util/signal-connection.cpp
index 7c74246..2d33116 100644
--- a/src/util/signal-connection.cpp
+++ b/src/util/signal-connection.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2013-2014 Regents of the University of California.
+ * Copyright (c) 2013-2015 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *