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.
Yes, I agree with you this is not as nice as we want... we need a finish event notification. Do we have some candidate in the Bokeh side? In the IPython notebook side, we can probably use the status of the Kernel (or something like that), but it is probably not specific enough to signalling the finish point we want...
In any case, this is not a final solution and maybe 15 seconds is too much too. Probably, we can lower it...