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/main.py b/main.py
index be5e313..531400c 100755
--- a/main.py
+++ b/main.py
@@ -1,4 +1,5 @@
 #!/usr/bin/env python
+# -*- coding:utf-8 -*-
 #
 # Copyright (C) 2008 The Android Open Source Project
 #