func Tr(path string) string {
	return DefaultEngine.Tr(path)
}
Tr provides default locale's translation of path.
package tr
var DefaultEngine *Engine
func init() {
	DefaultEngine = &Engine{}
}
const TrimEnd = true
func Init(path, defaultLocale string, trimOptional ...bool) error {
	trim := false
	if len(trimOptional) > 0 {
		trim = true
	}
	engine, err := NewEngine(path, defaultLocale, trim)
	if err != nil {
		return err
	}
	DefaultEngine = engine
	return nil
}