Added OOP class

I've added a OOP version of the main script. It works this way:

1. Create a new EmailVerifier instance assignating as params the email
to test and the email that will be used as source. Ex:

$verifier = new EmailVerifier('test@domain.com', 'source@domain.com');

2. Use validate() for get the result of the testing. It'll be returned
as an array with the status and the details of the testing.

I hope this small class could be part of the branch as an OOP development alternative.
Greetings !!!