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/rib.cpp b/daemon/rib/rib.cpp
index fe4db0b..1d002a1 100644
--- a/daemon/rib/rib.cpp
+++ b/daemon/rib/rib.cpp
@@ -27,8 +27,7 @@
 #include "fib-updater.hpp"
 #include "common/logger.hpp"
 
-namespace nfd {
-namespace rib {
+namespace nfd::rib {
 
 NFD_LOG_INIT(Rib);
 
@@ -496,5 +495,4 @@
   return os;
 }
 
-} // namespace rib
-} // namespace nfd
+} // namespace nfd::rib