Ordered includes

Change-Id: I193131cba5ff2ae7ad006eea2585f3dad4de4434
Reviewed-on: https://weave-review.googlesource.com/1295
Reviewed-by: Vitaly Buka <vitalybuka@google.com>

libweave/src/http_constants.cc

diff --git a/libweave/src/http_constants.cc b/libweave/src/http_constants.cc
index 445ff75..b6894a3 100644
--- a/libweave/src/http_constants.cc
+++ b/libweave/src/http_constants.cc
@@ -4,8 +4,8 @@
 
 #include "src/http_constants.h"
 
-#include <weave/provider/http_client.h>
 #include <weave/enum_to_string.h>
+#include <weave/provider/http_client.h>
 
 namespace weave {
 namespace http {