Mayday fails when run on a system lacking systemd

[brianredbeard]

When run on an OpenRC based system, mayday fails with the following:

$ ./mayday 
2017/01/14 20:46:23 loading config from /etc/mayday/default.json
2017/01/14 20:46:23 The name org.freedesktop.systemd1 was not provided by any .service files

We need to decide the proper behavior. (should it continue but exit non zero?, does it matter?)

[tschuy]

Fixed by #63