Refactor and modernize namespace declarations

Move all unit tests to namespace nfd::tests

Delete unused header core/algorithm.hpp

Change-Id: I5591f0c5f3bb5db67f8b45fae95471f8a555ca68
diff --git a/daemon/face/unix-stream-channel.cpp b/daemon/face/unix-stream-channel.cpp
index 7fb828b..2526d45 100644
--- a/daemon/face/unix-stream-channel.cpp
+++ b/daemon/face/unix-stream-channel.cpp
@@ -32,8 +32,7 @@
 #include <boost/filesystem.hpp>
 #include <sys/stat.h> // for chmod()
 
-namespace nfd {
-namespace face {
+namespace nfd::face {
 
 NFD_LOG_INIT(UnixStreamChannel);
 
@@ -148,5 +147,4 @@
   accept(onFaceCreated, onAcceptFailed);
 }
 
-} // namespace face
-} // namespace nfd
+} // namespace nfd::face