Added `update` method to `PlotlyList` and `PlotlyDict` + TestDrive NB.

Any object subclassing from PlotlyList or PlotlyDict is now able to use
a reasonable `update` method that makes sense for dealing with figures.

This is best shown by example. This commit also includes the
TestDrive.ipynb NB which runs through the basic functionality to date.
The last section is *Update* which discusses this new functionality.