Extending DOMAIN regex

Ensuring presence of the tld in the domain part.
without this modification a domain can be consider valid without the tld

e.g. : before an email like ```foo@bar``` will pass the validation which is not what we want.

PS : This is maybe not the best way to do it, but the need to fix this exist anyway.
If you have a better way to do this, help yourself, I just need that the library properly validates email address.

Thanks