Instructions for unzipping model.zip

[fireproofsocks]

This is minor, but it definitely threw some of us for a loop: when unzipping the model/model.zip, it's not clear that the contents of that need to be extracted into the model/ -- on some computers, it ended up extracting to model/model/ and that doesn't work. Moving the results of the extraction into the model/ directory seemed to make things work.

[githubharald]

The issue is already discussed in the "FAQ" section, but I think I'll add a short note about it in the "Run demo" section too.

EDIT: added instructions to the "Run demo" section now.

[fireproofsocks]

Ah, we did see that down in the FAQ shortly after posting the issue. It would probably be good to state it redundantly just for fools like us who didn't spot it the first time around.

Also, the cv2 package is completely weird... one student was able to download it in its python2 version, others could in no wise make the project's requirements fulfilled. Seems like something is odd about that package that might be worth mentioning in the instructions. Thanks!