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/y2017/control_loops/superstructure/hood/hood.cc b/y2017/control_loops/superstructure/hood/hood.cc
index 4f1a4eb..a8c1aa6 100644
--- a/y2017/control_loops/superstructure/hood/hood.cc
+++ b/y2017/control_loops/superstructure/hood/hood.cc
@@ -3,10 +3,7 @@
 #include "y2017/constants.h"
 #include "y2017/control_loops/superstructure/hood/hood_integral_plant.h"
 
-namespace y2017 {
-namespace control_loops {
-namespace superstructure {
-namespace hood {
+namespace y2017::control_loops::superstructure::hood {
 
 namespace chrono = ::std::chrono;
 
@@ -215,7 +212,4 @@
   return status_builder.Finish();
 }
 
-}  // namespace hood
-}  // namespace superstructure
-}  // namespace control_loops
-}  // namespace y2017
+}  // namespace y2017::control_loops::superstructure::hood