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/quaternion_utils.cc b/frc971/control_loops/quaternion_utils.cc
index bce78d0..dc5b411 100644
--- a/frc971/control_loops/quaternion_utils.cc
+++ b/frc971/control_loops/quaternion_utils.cc
@@ -3,8 +3,7 @@
 #include "Eigen/Dense"
 #include "Eigen/Geometry"
 
-namespace frc971 {
-namespace controls {
+namespace frc971::controls {
 namespace {
 
 double SinXoverX(double x) {
@@ -132,5 +131,4 @@
   return result;
 }
 
-}  // namespace controls
-}  // namespace frc971
+}  // namespace frc971::controls