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/control_loops/gaussian_noise.cc b/frc971/control_loops/gaussian_noise.cc
index ddfa0f3..1d0747c 100644
--- a/frc971/control_loops/gaussian_noise.cc
+++ b/frc971/control_loops/gaussian_noise.cc
@@ -1,7 +1,6 @@
 #include "frc971/control_loops/gaussian_noise.h"
 
-namespace frc971 {
-namespace control_loops {
+namespace frc971::control_loops {
 
 GaussianNoise::GaussianNoise(unsigned int seed, double stddev)
     : stddev_(stddev), generator_(seed), distribution_(0.0, 1.0) {
@@ -12,5 +11,4 @@
   return sample + (distribution_(generator_) * stddev_);
 }
 
-}  // namespace control_loops
-}  // namespace frc971
+}  // namespace frc971::control_loops