Add plugable logging providers

[ivz hh]

Hi, first of all, thank you so much for this wonderful project.

Are you going to support plugable logging providers? I hope to use journald as the default logging, so instead of using a log file, user can use syslog(), journald, or use systemd-cat command.

Do you have any plan to add this or are you open to pull-requests like this?

Thank you!