shuttle alpha-v0.5.1

1. Support Connection-Reuse.(e.g. Support FireFox)
2. Check New & Upgrade.
3. Move shuttle.yaml, logs and RespFiles to ~/Documents/shuttle/
4. Configuration: General -> set-as-system-proxy. (values: auto, manual)
5. English Document

升级指南：和之前版本一样覆盖默认配置文件，~/Documents/shuttle/目录下配置文件不存在时，启动Shuttle的时候会自动拷贝过去，以后就以~/Documents/shuttle/目录下配置文件为主