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.cc b/motors/peripheral/uart.cc
index 0617e3f..408bbfd 100644
--- a/motors/peripheral/uart.cc
+++ b/motors/peripheral/uart.cc
@@ -2,8 +2,7 @@
 
 #include <stdint.h>
 
-namespace frc971 {
-namespace teensy {
+namespace frc971::teensy {
 
 // Currently hard-coded for 8-bit + no parity + start bit + stop bit.
 void Uart::Initialize(int baud_rate) {
@@ -152,5 +151,4 @@
   }
 }
 
-}  // namespace teensy
-}  // namespace frc971
+}  // namespace frc971::teensy