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/zeroing/wrap.cc b/frc971/zeroing/wrap.cc
index 1a0504f..2e0e3bc 100644
--- a/frc971/zeroing/wrap.cc
+++ b/frc971/zeroing/wrap.cc
@@ -2,8 +2,7 @@
 
 #include <cmath>
 
-namespace frc971 {
-namespace zeroing {
+namespace frc971::zeroing {
 
 UnwrapSensor::UnwrapSensor(double sensor_offset, double sensor_range)
     : sensor_offset_(sensor_offset), sensor_range_(sensor_range) {
@@ -64,5 +63,4 @@
   return remainder(value - nearest, period) + nearest;
 }
 
-}  // namespace zeroing
-}  // namespace frc971
+}  // namespace frc971::zeroing