Nest all namespaces

The compiler supports this now.  We can type less going forward.
No functional changes.

Signed-off-by: Stephan Pleines <pleines.stephan@gmail.com>
Change-Id: I29d6fa4f9aacc0e381f1a7637294db0392466995
diff --git a/y2014/actors/autonomous_actor.cc b/y2014/actors/autonomous_actor.cc
index 07c6855..7486f47 100644
--- a/y2014/actors/autonomous_actor.cc
+++ b/y2014/actors/autonomous_actor.cc
@@ -17,8 +17,7 @@
 #include "y2014/queues/auto_mode_generated.h"
 #include "y2014/queues/hot_goal_generated.h"
 
-namespace y2014 {
-namespace actors {
+namespace y2014::actors {
 
 namespace chrono = ::std::chrono;
 namespace this_thread = ::std::this_thread;
@@ -432,5 +431,4 @@
   return true;
 }
 
-}  // namespace actors
-}  // namespace y2014
+}  // namespace y2014::actors