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/y2018/control_loops/superstructure/debouncer_test.cc b/y2018/control_loops/superstructure/debouncer_test.cc
index 2f56d56..ba3bd87 100644
--- a/y2018/control_loops/superstructure/debouncer_test.cc
+++ b/y2018/control_loops/superstructure/debouncer_test.cc
@@ -2,10 +2,7 @@
 
 #include "gtest/gtest.h"
 
-namespace y2018 {
-namespace control_loops {
-namespace superstructure {
-namespace testing {
+namespace y2018::control_loops::superstructure::testing {
 
 // Tests that the debouncer behaves as it should. This tests the following:
 // - The debouncer changes its internal state after the desired number of
@@ -53,7 +50,4 @@
 
   EXPECT_EQ(true, bouncer.current_state());
 }
-}  // namespace testing
-}  // namespace superstructure
-}  // namespace control_loops
-}  // namespace y2018
+}  // namespace y2018::control_loops::superstructure::testing