v0.5.1

Fix the definition of nested directives.

type CreateUserRequest struct {
	ApiVersion string `owl:"form=api_version"`
	User              // no directives defined here
}

type UpdateUserRequest struct {
	ApiVersion string           `owl:"form=api_version"`
	User       `owl:"body=xml"` // defined a "body" directive
}

Since no directives are defined on field CreateUserRequest.User, the directives defined in User struct are non-nested directives.

While UpdateUserRequest.User has a directive defined, thus, the directives defined in User struct are nested directives.