Add Catalan (es-CT) translations

Hi!
I've added the locales for Catalan (es-CT).

This is the flag:

![es-ct](https://cloud.githubusercontent.com/assets/1818725/3071898/8d024dd8-e2be-11e3-963d-45a895a7f152.png)

It's the same than https://github.com/refinery/refinerycms-i18n/blob/master/app/assets/images/refinery/icons/flags/catalonia.png
but renamed as es-CT.png (country code).