在学习git的时候，发现不能使用git clone从github.com下载，报了个ssl错误。
Cloning into cancan...
error: SSL certificate problem, verify that the CA cert is OK. Details:
error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed while accessing https://github.com/ryanb/cancan.git/info/refs
fatal: HTTP request failed
在网上找了一下，比较简单的解决办法：
git config --global http.sslVerify false