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/face/face.cpp b/tests/face/face.cpp
index e84ab03..dced528 100644
--- a/tests/face/face.cpp
+++ b/tests/face/face.cpp
@@ -9,7 +9,7 @@
 
 #include <boost/test/unit_test.hpp>
 
-namespace ndn {
+namespace nfd {
 
 BOOST_AUTO_TEST_SUITE(FaceFace)
 
@@ -22,4 +22,4 @@
 
 BOOST_AUTO_TEST_SUITE_END()
 
-} // namespace ndn
+} // namespace nfd