Status checking

Monit service has fields `status` and `status_hint`. If error occurs then monit sets bit in status field and resets same bit in status_hint.
I add constants and method for errors checking in status field.

Seems like passing in `code` is done purely for testing purposes; it'd be better to not do so and instead find some other way to set the status, probably by mocking a `Service` object.

Also I don't quite understand why `exact` was added; what's wrong with always being exact, or always being fuzzy?