Update animations to use jshtml

[charlesfrye]

Back when I first wrote the animations for this class, there was, AFAIK, no platform-independent way to generate replayable, interactive animations with mpl -- *nix systems could use temporary files and ffmpeg, with only a modicum of tooling, but that solution failed on Windows.

As of matplotlib 1.5 and, even more so, 2.1, that's no longer the case. See here for the most modern method, along with a link to an older one.

Would be great to be able to completely avoid the notebook magic, if at all possible, since it is stateful, confusing to new users, and it changes the rc. Will need to think on how to handle the 3-D plots.