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/y2016/vision/tools/blob_stream_replay.cc b/y2016/vision/tools/blob_stream_replay.cc
index 847f654..1c15259 100644
--- a/y2016/vision/tools/blob_stream_replay.cc
+++ b/y2016/vision/tools/blob_stream_replay.cc
@@ -18,8 +18,7 @@
 #include "y2016/vision/blob_filters.h"
 // #include "y2016/vision/process_targets.h"
 
-namespace y2016 {
-namespace vision {
+namespace y2016::vision {
 using namespace aos::vision;
 
 ::aos::vision::Vector<2> CreateCenterFromTarget(double lx, double ly, double rx,
@@ -573,8 +572,7 @@
   // count how many frames we miss in a row.
   int missed_count_ = 16;
 };
-}  // namespace vision
-}  // namespace y2016
+}  // namespace y2016::vision
 
 int main(int argc, char *argv[]) {
   using namespace y2016::vision;