WIP - use istanbul-require-hook

[jamestalmage]

This is just another exploratory PR.
Trying to figure out the best way to accommodate custom preprocessors.

istanbul-require-hook was mentioned here: istanbuljs/nyc#70.

I think it shoes great promise. Especially if altered to include hook combining/chaining with something similar to what was done here istanbuljs/nyc#65

I think we are nearing a real solution. Until a clear winner emerges from the solutions proposed in istanbuljs/nyc#70, I think I will fork istanbul-require-hook with some changes specific to what we need.

[ariporad]

Two things:

1. It's called istanbul-lib-hook, not istanbul-require-hook, FYI
2. I think that it would be worthwhile to use pirates instead, as istanbul-lib-hook will (hopefully) soon just be a wrapper around pirates.

[jamestalmage]

@ariporad - yep, this was an exploratory thing I did when that whole discussion kicked off.

I am going to be opposed to integrating pirates in any projects until danez/pirates#5 is resolved.

[ariporad]

@jamestalmage: Fair. I've just posted an update in that issue, in the interest of now flooding this one.