sensors/zones: place in namespace and cleanup

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: I527dbc8477a232945f696227a7b0b2adbee45175
diff --git a/test/writeinterface_mock.hpp b/test/writeinterface_mock.hpp
index d25e332..0aed48d 100644
--- a/test/writeinterface_mock.hpp
+++ b/test/writeinterface_mock.hpp
@@ -4,6 +4,9 @@
 
 #include <gmock/gmock.h>
 
+namespace pid_control
+{
+
 class WriteInterfaceMock : public WriteInterface
 {
   public:
@@ -14,3 +17,5 @@
 
     MOCK_METHOD1(write, void(double));
 };
+
+} // namespace pid_control