Update readme, add some todos, add example svg

pkg/get.go

@@ -16,6 +16,8 @@ type GetCfg struct {
 
 // Get executes the "git get" command.
 func Get(c *GetCfg) error {
+	// TODO: show something when no args
+
 	if c.URL != "" {
 		return cloneSingleRepo(c)
 	}

pkg/list.go

@@ -51,6 +51,7 @@ func List(c *ListCfg) error {
 	case cfg.OutDump:
 		printer = &print.DumpPrinter{}
 	default:
+		// TODO: fix
 		return fmt.Errorf("invalid --out flag; allowed values: %v", []string{cfg.OutFlat, cfg.OutTree, cfg.OutSmart})
 	}