message: add __version__ back
diff: @@ -3,7 +3,8 @@ from __future__ import division
  from __future__ import print_function
  from __future__ import unicode_literals
  -from .onnx_pb2 import *
  +from .onnx_pb2 import * # noqa
  +from .version import version as __version__ # noqa
  import sys
  