Use a Scheduling library to schedule background tasks

[andrewtobin]

Use something like http://quartznet.sourceforge.net/ to schedule the background polling of the data fetchers.

[shiftkey]

Suggested API for extensions here: https://github.com/Code52/jibbr/blob/master/Jabbot.CommandSprockets/IAnnounce.cs

Simple scheduler for testing console-based bot: https://github.com/Code52/jibbr/blob/master/Jabbot.ConsoleBotHost/Scheduler.cs