src: Changing namespace ndn to namespace nfd

Also, this commit imports used classes from ::ndn namespace (from
NDN-CPP library) directly to ::nfd namespace.

refs: #1163

Change-Id: I9cc9d72e00af495b4ed0c84e6d418a7c9ba986cb
diff --git a/tests/core/time.cpp b/tests/core/time.cpp
index 64ad830..6d0db3f 100644
--- a/tests/core/time.cpp
+++ b/tests/core/time.cpp
@@ -8,7 +8,7 @@
 
 #include <boost/test/unit_test.hpp>
 
-namespace ndn {
+namespace nfd {
 
 BOOST_AUTO_TEST_SUITE(CoreTime)
 
@@ -44,4 +44,4 @@
 
 BOOST_AUTO_TEST_SUITE_END()
 
-} // namespace ndn
+} // namespace nfd