First working version of automated execution of notebooks in example folder.

Very WIP... I will work more on this in the next days...

Edit: No longer a WIP.
I do not pretend to be a mirror... I agree with you it can not be easily reproducible locally.
Btw, this implementation only makes sense locally, because you have to check the pics generated from the notebooks. So, my first aim is to provide that... with passing test at travis, of course...