YangYu

so may someone give a review and merge it?

@1995eaton hi may you pls merge this?

@henvic hi may you pls give more details about the insecure problem happy to know about this : )

不错严重支持，如果时间允许，希望能参加一下

@JacksonTian，朴大也是蛮拼的，这么晚还在

var digest = require('http-digest-client')('username', 'password');

官方文档提到如果用本地的目录缓存需要自己实现锁，不然会有一些隐患