Add a subsection for fun?

Because fun is fun!

I am following up on this thread: https://groups.google.com/forum/#!searchin/scikit-image/Fun$20with$20skimage/scikit-image/vrPzanJ42rs/eYEnufuGurcJ

@stefanv @jni @JDWarner Let me know if all this makes any sense. If so, I'll expand.

0) The swirl transformation on Mona Lisa is an example I have been meaning to document.

1) I don't know what the Embedded Face Detection example is, but @jni mentioned it -- Could you point me to it?   

2) The example showing interactivity within an IPython Notebook was the one which triggered the idea for this subsection.

3) I wanted to follow @JDWarner's idea on Instagram-like filters + I have been meaning to include Fabio...  Which took me a little off track, maybe.  I used http://www.google.com/advanced_image_search to get pictures 'labeled for reuse with modification'.  I picked this JPG file http://s2.hubimg.com/u/6335273_f496.jpg so you cannot simply import it from `imread` (as documented here: http://nbviewer.ipython.org/gist/rsignell-usgs/3918576).