sensors/zones: place in namespace and cleanup

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: I527dbc8477a232945f696227a7b0b2adbee45175
diff --git a/pid/pidcontroller.cpp b/pid/pidcontroller.cpp
index e3eaaff..e7a4ad1 100644
--- a/pid/pidcontroller.cpp
+++ b/pid/pidcontroller.cpp
@@ -27,6 +27,9 @@
 #include <thread>
 #include <vector>
 
+namespace pid_control
+{
+
 void PIDController::process(void)
 {
     double input;
@@ -78,3 +81,5 @@
 
     return;
 }
+
+} // namespace pid_control