Added animated filtering

Rewrote some of the chapter examples to use animated plots. Makes
it so much easier to see how the filter is performing.

code/book_plots.py

@@ -47,6 +47,7 @@ def interactive_plot(close=True, fig=None):
     if fig is None:
         fig = plt.figure()
     yield
+    plt.tight_layout()
     if close:
         end_interactive(fig)