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.
@bryevdv, ok, we can test only the `ipynbs` outside the `plotting/notebook` folder... I think there are two or three right now,  and let's create the "all-notebooks" flag to use it locally.

@mattpap, yes I saw the ``--timeout``, I will use this as default value in `test.js`...