Support docker for mac

[wweir]

Docker for Mac is a useful toolset, especially kubernetes support.

I use the cow transform socks5(go-shadowsocks2) protocol into HTTP(s) proxy and set the HTTP proxy in docker for mac. Then deploy kubernetes in docker for mac, the docker hangs forever.

After that, I install shadowsocksX-ng which integrate proxioy as http proxy tool, the kubernetes deployed correctly.

Then, I try docker pull k8s.gcr.io/pause-amd64:3.0 at these two networks environment, Wireshark shows the cow hangs a connection.