Make it possible to swap out the default notification mechanism.
Turns out that strconv.ParseBool doesn't accept yes and no as boolean values, so replaced yes and no with true and false in the sample config file.
Add support for rules that should be polled periodically.
Add SetUrlFetcher method to engine.
Change default poll time offset to 24:00 UTC.
Add some more debugging info about when rules will run if they are not included in the set of rules ready for polling.
Refactor Config into an interface that is implemented by the FileConfig structure. This will help with testing the Engine class by making it easier to mock out Config.
Greatly increased test coverage.