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/can_logger/asc_logger.cc b/frc971/can_logger/asc_logger.cc
index 96b2e96..6848938 100644
--- a/frc971/can_logger/asc_logger.cc
+++ b/frc971/can_logger/asc_logger.cc
@@ -2,8 +2,7 @@
 
 #include <linux/can.h>
 
-namespace frc971 {
-namespace can_logger {
+namespace frc971::can_logger {
 
 AscLogger::AscLogger(aos::EventLoop *event_loop, const std::string &filename)
     : output_(filename), event_loop_(event_loop) {
@@ -138,5 +137,4 @@
   file << "\n";
 }
 
-}  // namespace can_logger
-}  // namespace frc971
+}  // namespace frc971::can_logger