[bug report]pouch client doesn't use tcp connection about pouch

[allencloud]

I found that in every command implementation, there is client, err := client.New("") which is root cause of ignoring input -H data. Like:

// Run is the entry of stop command.
func (s *StopCommand) Run(args []string) {
	container := args[0]

	client, err := client.New("")
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to new client: %v\n", err)
		return
	}

What about it? Could you help to solve this? @Ace-Tang

[allencloud]

I submit a PR of #84 to fix this, PTAL. 🍺