composer: phpunit 4.8 (#940)
composer: phpunit 4.8 (#940)

switch from 4.7 to 4.8 (latest stable) of phpunit
nawawi/PHPMailer,pingyen/PHPMailer,ravisorg/PHPMailer,PHPMailer/PHPMailer,jimjag/PHPMailer,ravisorg/PHPMailer,jimjag/PHPMailer,PHPMailer/PHPMailer,Synchro/PHPMailer,nawawi/PHPMailer,Synchro/PHPMailer,pingyen/PHPMailer