Nested Struct Scanning

This release adds the ability to scan to a nested struct.

rows, err := db.Query(`
	SELECT person.id,person.name,company.name FROM person
	JOIN company on company.id = person.company_id
	LIMIT 1
`)

var person struct {
	ID      int    `db:"person.id"`
	Name    string `db:"person.name"`
	Company struct {
		Name string `db:"company.name"`
	}
}

err = scan.RowStrict(&person, rows)

err = json.NewEncoder(os.Stdout).Encode(&person)
// Output:
// {"ID":1,"Name":"brett","Company":{"Name":"costco"}}