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.hpp b/daemon/rib/service.hpp
index 8928011..02e1914 100644
--- a/daemon/rib/service.hpp
+++ b/daemon/rib/service.hpp
@@ -38,8 +38,7 @@
 #include <ndn-cxx/transport/transport.hpp>
 #include <ndn-cxx/util/scheduler.hpp>
 
-namespace nfd {
-namespace rib {
+namespace nfd::rib {
 
 class Readvertise;
 
@@ -121,7 +120,6 @@
   RibManager m_ribManager;
 };
 
-} // namespace rib
-} // namespace nfd
+} // namespace nfd::rib
 
 #endif // NFD_DAEMON_RIB_SERVICE_HPP