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/control_loops/jacobian_test.cc b/frc971/control_loops/jacobian_test.cc
index 57c9d7f..5606004 100644
--- a/frc971/control_loops/jacobian_test.cc
+++ b/frc971/control_loops/jacobian_test.cc
@@ -2,9 +2,7 @@
 
 #include "gtest/gtest.h"
 
-namespace frc971 {
-namespace control_loops {
-namespace testing {
+namespace frc971::control_loops::testing {
 
 ::Eigen::Matrix<double, 4, 4> A = (::Eigen::Matrix<double, 4, 4>() << 1, 2, 4,
                                    1, 5, 2, 3, 4, 5, 1, 3, 2, 1, 1, 3, 7)
@@ -35,6 +33,4 @@
   EXPECT_TRUE(NewB.isApprox(B));
 }
 
-}  // namespace testing
-}  // namespace control_loops
-}  // namespace frc971
+}  // namespace frc971::control_loops::testing