sensors/zones: place in namespace and cleanup

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: I527dbc8477a232945f696227a7b0b2adbee45175
diff --git a/sensors/buildjson.hpp b/sensors/buildjson.hpp
index 979cd87..ee82381 100644
--- a/sensors/buildjson.hpp
+++ b/sensors/buildjson.hpp
@@ -9,6 +9,9 @@
 
 using json = nlohmann::json;
 
+namespace pid_control
+{
+
 /**
  * Given a json object generated from a configuration file, build the sensor
  * configuration representation. This expecteds the json configuration to be
@@ -19,3 +22,5 @@
  */
 std::map<std::string, struct conf::SensorConfig>
     buildSensorsFromJson(const json& data);
+
+} // namespace pid_control