ENH: add spatio-temporal clustering example for sensor data

MNE Python has been capable of this for at least three months. Time to expose it :)

It finds 6 clusters using an F-test, which is justified here as we do not have any ties on a first level analysis
(permuiting condition order does not affect hypotheses).
Here's two of them:

![screenshot 2014-11-05 22 16 44](https://cloud.githubusercontent.com/assets/1908618/4926316/6ff0a2ca-6532-11e4-9f46-e584b08de3e0.png)

For conveniences, I've added the neigho(u)r files from fieldtrip, slightly renamed to make a difference.
Thanks for the attendees of our Paris workshop who motivated me to give this example, especially @matthew-tucker


cc @agramfort
2 spaces after layout

also I'd rather avoid this extra depth of modules by just putting layout.py templates/ same for montage. The put the data files in templates/data/layouts/ templates/data/montages/ templates/data/neighbors/ 

..templates.layouts.layout is redundant and ..templates.layout is clear enough