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.
> My laptop is a core i3 with 4gb of ram, so probably I am a good mirror of travis

Not really, because if it was dependent on machine/vm speed, then you would see this in every example, but there are fluctuations, which I attribute to scheduling algorithm, e.g. paying customers come first, so this is something you can't reproduce locally, at least not without some effort (you could play with task scheduler's configuration).