WIP - catch fatal errors during execution

![fatal-catching](https://cloud.githubusercontent.com/assets/237866/5268102/a70677a4-7a4e-11e4-82b6-a65ef30ae715.gif)

This is submitted mostly as a talking point.

It 'works' but feels dirty. Is it too dirty? It's a feature I'm not sure can be done in a non-dirty way.

Note: only fatals that occur during an Example are caught properly right now, other fatals (phpspec runtime issues or spec parse errors) may cause unexpected results