set default file encoding to utf-8

There's no reason to support any other encoding in these files.
This only affects the files themselves and not streams they open.

Bug: https://crbug.com/gerrit/10418
Change-Id: I053cb40cd3666ce5c8a0689b9dd938f24ca765bf
diff --git a/editor.py b/editor.py
index 7980f2b..b761eb5 100644
--- a/editor.py
+++ b/editor.py
@@ -1,3 +1,4 @@
+# -*- coding:utf-8 -*-
 #
 # Copyright (C) 2008 The Android Open Source Project
 #