Refactor how to setup mailer.

Signed-off-by: crynobone <crynobone@gmail.com>
Merge branch '2.1' into 2.2

Signed-off-by: crynobone <crynobone@gmail.com>

Conflicts:
	src/Notifier/Mailer.php
Fixes testcase

Signed-off-by: crynobone <crynobone@gmail.com>
Merge branch '2.2'