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/motors/peripheral/uart_buffer_test.cc b/motors/peripheral/uart_buffer_test.cc
index 223c029..0ee5a49 100644
--- a/motors/peripheral/uart_buffer_test.cc
+++ b/motors/peripheral/uart_buffer_test.cc
@@ -2,9 +2,7 @@
 
 #include "gtest/gtest.h"
 
-namespace frc971 {
-namespace teensy {
-namespace testing {
+namespace frc971::teensy::testing {
 
 // Tests that using PushSpan with single characters works correctly.
 TEST(UartBufferTest, PushSpanSingle) {
@@ -281,6 +279,4 @@
   }
 }
 
-}  // namespace testing
-}  // namespace teensy
-}  // namespace frc971
+}  // namespace frc971::teensy::testing