Fixed specs and slug for multi-language

Hi,
in the first commit I've fixed the specs with the new Globalize gem.
In the second commit I've added the possibility to create a translated object with all translations in one single step. This is useful to integrate with ActiveAdmin (though it's not tested directly with that).
I've tested the new feature. Let me know if you need any explaination. Cheers!
Hi, I'm very sorry for having abandoned this PR, but many things changed since I started :)
I hope this could still be of any use. Anyway, now I can spend some time on this.

You were absolutely right about the ```.to_a``` which I have removed. Instead I don't understand what do you think to change in the ```map```, can you explain that again please?