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/dummy-face.hpp b/tests/face/dummy-face.hpp
index a960380..a58a3ee 100644
--- a/tests/face/dummy-face.hpp
+++ b/tests/face/dummy-face.hpp
@@ -9,7 +9,7 @@
 
 #include "face/face.hpp"
 
-namespace ndn {
+namespace nfd {
 
 /** \class DummyFace
  *  \brief provides a Face that cannot communicate
@@ -34,6 +34,6 @@
   }
 };
 
-} // namespace ndn
+} // namespace nfd
 
 #endif // TEST_FACE_DUMMY_FACE_HPP