nuster v5.0.1.21 发布，高性能缓存服务器

nuster 是一个基于 HAProxy 的高性能 HTTP 缓存服务器和 RESTful NoSQL 缓存服务器，既可以用作类似 Varnish 或者 Nginx 那样的 HTTP 缓存服务器，来缓存动态或者静态的 HTTP 资源，也可以用作 RESTful NoSQL 缓存服务器, 用 HTTP POST/GET/DELETE 来 添加 /取得 /删除 Key/Value。 

中文 readme：https://github.com/jiangwenyuan/nuster/blob/master/README-CN.md

本次是基于最新 HTX 版的 HAProxy 的全新重新以及重构，带来了很多性能提升，支持客户端和 Proxy，Proxy和后端服务器的 HTTP2 连接等。

A complete refactored version based on HTX version of HAProxy. Lots of changes, updates, improvements, to name a few:

• Add nuster manager, moved purge-method and uri to manager, support both cache and nosql
• Update new stats, support both cache and nosql
• Update purger, add basic and advance purger, support creating key based on rule
• Add memory on|off, disk on|off|sync, in form of backend store, more easier to add new store
• Create new key, avoided redundant compuating, improved performance
• Unified lots of components