add "cluster ls", put "status" into "cluster status" (#5)

cmd/root.go

@@ -72,7 +72,6 @@ func Main() int {
 		},
 
 		Commands: []*cli.Command{
-			Status(conf),
 			Search(conf),
 			Index(conf),
 			Snapshot(conf),
@@ -81,7 +80,12 @@ func Main() int {
 
 		Before: func(ctx context.Context, cmd *cli.Command) (context.Context, error) {
 			if err := conf.Init(); err != nil {
-				return nil, err
+				if len(os.Args) > 1 {
+					return nil, err
+				} else {
+					fmt.Println(cmd.UsageText)
+					return nil, nil
+				}
 			}
 
 			log.Init(conf)