Implement Issue #571

Allow estmp connection options to be set.  Can be used to allow ssl / tls to use self-signed certificates with the following "options" set:  array('ssl' => array('allow_self_signed' => true, 'verify_peer' => false)).

Reference:
http://stackoverflow.com/questions/26896265/php-swiftmailer-using-starttls-and-self-signed-certificates