[WIP] Glass brain visualisation

This pull request is WIP for now and was only opened to get some feedback, both code-wise and visualisation-wise.

Here is how it looks like atm:
![glass_brain](https://cloud.githubusercontent.com/assets/1680079/4418755/d5d028da-4562-11e4-9a20-95fda9036a6b.png)

The code to generate the plots is there.