Cocos2d-x lua internationalization helper

IMPORTANT: this libary need lua module from https://github.com/kaishiqi/I18N-Gettext-Supported. require 'i18n' should work.

This library is only wrap around that, so you should read documentation to both libraries.

Why do you need this wrap?

1. Language magement: you can set mapping between languages and files. Also, you can set prefix for all files.
2. Better interface: now you have got object-oriented metamethod-based API. There is no more tons of ugly methods.
3. Full cocos2d-x integration: functions for saving, loading and using system language is aviable.

Documentation

See DOCUMENTATION.md for help.

TODO list

1. make auto-testing with Travis-ci
2. make manual-testing with Cocos2d-x
3. write examples