Translated attributes should reflect I18n.locale change

When accessing localized attribute it should always return value according to current `I18n.locale` settings.

I should be able to write:
```
I18n.locale = :en
post.title #post.title_en

I18n.locale = :fr
post.title #post.title_fr
```


`locales_to_try` in `LocalizedReader` is cached, so code above don't work. I've removed caching.