[WIP] @orta => Last-minute hook

Fixes #9.

There are tests included, but I'd like to be more thorough and have tests that verify more than just the fact that the closure is executed, but have tests that demonstrate how one could use it. Also need to update the README. 

- [ ] More tests
- [ ] Update README

![](http://25.media.tumblr.com/37d3f5e82bc6816dbdb1ada6f9499952/tumblr_mtvtnhtYt01qhry52o1_500.gif)