Switch to dep for dependency management

vendor/github.com/jessevdk/go-flags/arg.go

@@ -12,6 +12,12 @@ type Arg struct {
 	// A description of the positional argument (used in the help)
 	Description string
 
+	// The minimal number of required positional arguments
+	Required int
+
+	// The maximum number of required positional arguments
+	RequiredMaximum int
+
 	value reflect.Value
 	tag   multiTag
 }