Make gn directory importable in python

This will make it possible to do
>>> from gn import gn_to_bp
instead of:
>>> sys.path.append('gn')
>>> import gn_to_bp
in the new Android autoroller

BUG=skia:5538

Change-Id: I4fe851247ab6dd5bc553b8315ad91281819fbc7e
Reviewed-on: https://skia-review.googlesource.com/9897
Reviewed-by: Eric Boren <borenet@google.com>
Commit-Queue: Ravi Mistry <rmistry@google.com>
diff --git a/gn/__init__.py b/gn/__init__.py
new file mode 100644
index 0000000..5664828
--- /dev/null
+++ b/gn/__init__.py
@@ -0,0 +1,3 @@
+# Copyright (c) 2017 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.