[WIP] Add IPython notebooks with PyClaw versions of FVM book examples

So far, I have just ported the first example (simple waves for acoustics, from Chapter 3).  Comments on the notebook are welcome.  I included a few comments explaining bits of code, but no mathematical discussion since that is in the book.  Afterward, I thought that it might be worth putting an explanation into the notebook so that it is more self-contained.  Thoughts?