Callback Mechanisms

[anfleene]

Somehow we need to figure out how to plug in callbacks of some sort so that we can pull out things like posting to pivotal tracker/jira, running zapier hooks etc.

I'm thinking if we build a generic callback structure for like before/after hooks to just run a given command in the config we could probably get 90% of what we want.

[NickLaMuro]

#16 Kind of does this for us, but we can do better I think. Leaving this open.