Created by: oraoto

In https://github.com/PaddlePaddle/VisualDL/pull/518 , protobuf was changed to 3.1.0 which break the Windows build.

To build protobuf 3.1 in Windows, an upstream patch https://github.com/protocolbuffers/protobuf/commit/1d2c7b6c7376f396c8c7dd9b6afd2d4f83f3cb05 is required.

This PR use the latest version of protobuf 3.1.x which includes the required patch. Python 3.5, 3.7, 3.7 are testd: AppVeyor