added #99 required_locales for 1.X versions

Hi,

I added required_locales option for 1.x versions because gedmo extensions bundle is not compatible with gedmo extions wid-v2.4@dev yet so there is no way to install 2.x version of your bundle on symfony2.5 for now and required_locales is a very blocking missing functionnality.

I just applied your diff (adapted for 1.x) of #99

I could only test it with Gedmo so if you have time, you can test it without Gedmo and merge with 1.x, it can be usefull for others i think.

And thanks for your great job !