[FR] Update Christmas name in french that was wrong from 'Nöel' to 'Noël'

Hello!

Thanks for this very nice gem!

Our team noticed that the name for Christmas holiday was badly translated in French.
So here is a fix to have the correct name (corrected 'Nöel' to 'Noël')

I also specified the ruby version to use to build the ruby files in the README. Coz it messes everything up with ruby-1.8.7.

Have a great day.
Paul