Localize Middleware language-detection bug

[lianguan]

MiddleWare/Localize line 60:

foreach ($supportedLanguages as $language) {
            $language = substr($language, 0, 2);

            if (isset($this->langs[$language])) {
                $userLanguage = $language;
                break;
            }
        }

the code above have two bugs:

1. It dosn't distinguish zh-CN and zh-TW.
2. both language package of zh-CN and zh-TW contain '-', but the spliter of browser's accept-language is '_'.

so, I think the right code is:

$language = str_replace('_', '-', $language);