树莓派更换源
系统版本：2017-11-29-raspbian-stretch-lite 编辑/etc/apt/sources.list： #deb http://mirrordirector.raspbian.org/raspbian/ stretch main contrib non-free rpi # Uncomment line below then 'apt-get update' to enable 'apt-get source' #deb-src http://archive.raspbian.org/