update .clang-format

Added the header inclusion order to the .clang-format file generated
these changes.

Change-Id: I4f51a20f469de431ee6a5ba78e3f4da39c980fab
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/src/event_manager.cpp b/src/event_manager.cpp
index 57a8478..874c5a8 100644
--- a/src/event_manager.cpp
+++ b/src/event_manager.cpp
@@ -15,8 +15,10 @@
  */
 
 #include "config.h"
-#include "event.hpp"
+
 #include "event_manager.hpp"
+
+#include "event.hpp"
 #include "event_serialize.hpp"
 
 #include <experimental/filesystem>