httpclient-x Apache HttpComponents Client框架扩展

Reference: [1] HttpClient Overview

Change log:

2014.11.06 [NEW] KeepAliveHttpClients - 增加基于连接管理器和Keep-Alive来创建HttpClients的工厂方法

2014.11.05 [NEW] KeepAliveHttpClientsTest - 基于Keep-Alive HTTP并发连接有效及失效过期而被关闭的测试策略

2014.11.03 [NEW] CustomUserTokenHandler - 自定义的用户标记处理器(UserTokenHandler)实现

2014.11.01 [NEW] KeepAliveHttpClients - 创建基于Keep-Alive的HttpClient客户端