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/action_joystick_input.cc b/frc971/input/action_joystick_input.cc
index dfd229e..ae3346c 100644
--- a/frc971/input/action_joystick_input.cc
+++ b/frc971/input/action_joystick_input.cc
@@ -8,8 +8,7 @@
 
 using ::frc971::input::driver_station::ControlBit;
 
-namespace frc971 {
-namespace input {
+namespace frc971::input {
 
 void ActionJoystickInput::RunIteration(
     const ::frc971::input::driver_station::Data &unsorted_data) {
@@ -74,5 +73,4 @@
   AutoEnded();
 }
 
-}  // namespace input
-}  // namespace frc971
+}  // namespace frc971::input