Add support for NativeMailerHandler

[david-fuehr]

When emails for log events are sent, the \Monolog\Handler\NativeMailerHandler allows a more flexible use of the sendmail command as \Monolog\Handler\SwiftMailerHandler does.

Because the NativeMailerHandler evaluates the php ini setting sendmail_path, the way emails are sent can be configured per host. This allows for example the use of mailhog in testing enviroments.

UAC

1. It is possible to configure \Monolog\Handler\NativeMailerHandler as mailer handler in loggers section