laravel/framework — pull request #6166 by overtrue (2014-10-21 11:05:59+00:00)
Title: Fix Str::length return errors value when dealing with multi-byte length string

examle:
```php
$str = '这是一个长度47个字符的中文字符串';

echo mb_strlen($str, 'UTF-8'); // 17

echo Illuminate\Support\Str::length($str);// 47
```