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/rib/service.cpp b/daemon/rib/service.cpp
index d850ed2..1634ef9 100644
--- a/daemon/rib/service.cpp
+++ b/daemon/rib/service.cpp
@@ -38,8 +38,7 @@
 #include <ndn-cxx/transport/tcp-transport.hpp>
 #include <ndn-cxx/transport/unix-transport.hpp>
 
-namespace nfd {
-namespace rib {
+namespace nfd::rib {
 
 NFD_LOG_INIT(RibService);
 
@@ -262,5 +261,4 @@
   }
 }
 
-} // namespace rib
-} // namespace nfd
+} // namespace nfd::rib