pip install 过程出现 Failed building wheel for greenlet，如下图： <img width="654" alt="2018-04-22 12 10 42" src="https://user-images.githubusercontent.com/5173739/39086298-0a335cf6-45c2-11e8-807f-cf883aec4ed1.png"> <img width="774" alt="2018-04-22 12 11 03" src="https://user-images.githubusercontent.com/5173739/39086299-0c3dc69e-45c2-11e8-838e-1d9d5598bbb6.png">
pip install 过程出现 Failed building wheel for greenlet，如下图：
