fix: get proxy ip also need user-agent

[Monsterstars]

执行：
python DirScan.py baidu.com ./dictionary/

报错：

      ___  __       _  _
     |__ \/_ |     | |(_)
        ) || |   __| | _  _ __   ___   __ _   ___  _ __
       / / | |  / _` || || '__| / __| / _` | / __|| '_ \
      / /_ | | | (_| || || |    \__ \| (_| || (__ | | | |
     |____||_|  \__,_||_||_|    |___/ \__,_| \___||_| |_|

输入的路径为./dictionary/
......
urllib3.exceptions.MaxRetryError: HTTPSConnectionPool(host='www.kuaidaili.com', port=443): Max retries exceeded with url: /free/inha/1/ (Caused by ProxyError('Cannot connect to proxy.', RemoteDisconnected('Remote end closed connection without response')))

原因：请求www.kuaidaili.com需要带上UA