Python module and packages doc python version clarification

[moar55]

I think it should be clarified that urllib.urlopen won't work in python 3, and for python 3 users should use urllib.request.urlopen.

[joyceerhl]

Hi @ronreiter , I would be happy to submit a PR for this if still relevant!

[ronreiter]

@joyceerhl it is! However, @victor-ru has some more information on how to make the Python 3 Ideone API work. I also want the Ideone API key not to be committed in the code but rather handed out by me to whoever wants to run this on his computer, and by default a clean check out will run the code on the interactive tutorials server.