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/frc971/input/driver_station_data.cc b/frc971/input/driver_station_data.cc
index 18d96fd..06d2d69 100644
--- a/frc971/input/driver_station_data.cc
+++ b/frc971/input/driver_station_data.cc
@@ -2,9 +2,7 @@
 
 #include "glog/logging.h"
 
-namespace frc971 {
-namespace input {
-namespace driver_station {
+namespace frc971::input::driver_station {
 
 Data::Data() : current_values_(), old_values_() {}
 
@@ -119,6 +117,4 @@
   return current_values_.joysticks[axis.joystick() - 1].axis[axis.number() - 1];
 }
 
-}  // namespace driver_station
-}  // namespace input
-}  // namespace frc971
+}  // namespace frc971::input::driver_station