We should be able to check that a service is running

[majormoses]

Rather than having to match the process's command with all its args etc we should have a seperate check to be able to check sysvinit, upstart, and systemd style services status.

Created from #37 (comment)

[majormoses]

runnit would also be a nice enhancement.

[Evesy]

Were you thinking of a single check that supports/runs against all these service managers (i.e. via a flag to specify the provider) or separate checks for each different service manager?

[majormoses]

ideally a flag would work but depending on how much difference there is it might make sense to do one per provider, if we go that route I'd like whatever common logic to be pushed into a lib.