Prepare 0.5.0 release

Small fix to properly handle ndnsec identity check message and also update copyright years in several files.

Change-Id: I1fae8749f7d755f4af1ccca519c236480ff3f824
diff --git a/minindn/util.py b/minindn/util.py
index dd46557..8584ffc 100644
--- a/minindn/util.py
+++ b/minindn/util.py
@@ -1,6 +1,6 @@
 # -*- Mode:python; c-file-style:"gnu"; indent-tabs-mode:nil -*- */
 #
-# Copyright (C) 2015-2019, The University of Memphis,
+# Copyright (C) 2015-2020, The University of Memphis,
 #                          Arizona Board of Regents,
 #                          Regents of the University of California.
 #