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/motors/simple_receiver.cc b/motors/simple_receiver.cc
index bb10353..2ae0c9b 100644
--- a/motors/simple_receiver.cc
+++ b/motors/simple_receiver.cc
@@ -19,8 +19,7 @@
 #include "motors/seems_reasonable/spring.h"
 #include "motors/util.h"
 
-namespace frc971 {
-namespace motors {
+namespace frc971::motors {
 namespace {
 
 using ::frc971::constants::ShifterHallEffect;
@@ -799,5 +798,4 @@
   }
 }
 
-}  // namespace motors
-}  // namespace frc971
+}  // namespace frc971::motors