Steve Witham's Twitter Puddle solutions

Hi, 

This contains an iiPython notebook and a png illustration.
The link in `index.html` is to a URL at [http://nbviewer.ipython.org], which then links to the copy of the notebook in **my** fork of the github repo.  The link to the illustration within the notebook is also to my fork.

I think thiat's all okay as is.  People will by default be directed to my copies, but I will keep them around, plus there will be good copies in the [https://github.com/BostonPython/puzzles] repo also.

But, it is also okay with me if you want to point those links into the `BostonPython` repo.

 --Steve