客户端接口，关于用户的操作
This class object is the super class that every library in CodeIgniter will be assigned to.
$instance : object
Reference to the CI singleton
__construct() : void
Class constructor
get_instance() : object
Get the CI singleton
create_unique()
唯一token
login()
登录
weixin()
微信授权
oauth()
微信授权回调函数
qq()
callback()
third_reg()
common( $data)