New method to create Shadowsocks service on GC

New method to create Shadowsocks service on google cloud.

1. create instance centos7 with minor cpu.
2. sudo
3. #yum install python-setuptools && easy_install pip
   #pip install shadowsocks
   #ssserver -p 1194 -k xxxxxx(pwd) -m rc4-md5&
4. http://old.tool.chinaz.com/port/ to check if the port is usable.
5. firewall rule create for all instances in the network allowing
   0.0.0.0/0 to access port 1194
   
6. configure shadowsocks agent on devices.