Add kconv filter to support i18n(CJKV) data.

Dear sir.

Thank you very much for your hack. The gem is absolutely cool, simple and useful.
I would like to contribute you to support i18n csv data in this gem. It is just only two line and the 'kconv' lib is very very coherent.

Thank you very much and hope you good hack.

Yours sincerely.
Bungo Tamari