Language detection isn't correct

[Leonidius20]

For example, my server's language is Russian (rus), but this plugin uses English, because Russian translation file's name is "lang_ru". You need to rename the file into "lang_rus" or to change language detection mechanism, so that it checks 2 first letters of the language's name, not three.

[kochurovro]

Kindly check it https://github.com/EconomyS/EconomyAPI/pull/12