使用guzzlehttp的时候报如下错误：
cURL error 60: SSL certificate problem: unable to get local issuer certificate
解决方法：
Follow this link: http://curl.haxx.se/ca/cacert.pem
Copy the entire page and save it in a: "cacert.pem"
Then in your php.ini file insert or edit the following line:
curl.cainfo = "[pathtothisfile]\cacert.pem"
