sensors/zones: place in namespace and cleanup

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: I527dbc8477a232945f696227a7b0b2adbee45175
diff --git a/pid/fancontroller.cpp b/pid/fancontroller.cpp
index dd26d16..41f24da 100644
--- a/pid/fancontroller.cpp
+++ b/pid/fancontroller.cpp
@@ -23,6 +23,9 @@
 #include <algorithm>
 #include <iostream>
 
+namespace pid_control
+{
+
 std::unique_ptr<PIDController>
     FanController::createFanPid(ZoneInterface* owner, const std::string& id,
                                 const std::vector<std::string>& inputs,
@@ -140,3 +143,5 @@
 
     return;
 }
+
+} // namespace pid_control