Add experiment annotation to all examples that are meant to run

[xogeny]

I should add experiment annotations to all the examples. However, when including
these examples into the text of the book, I'll typically want to strip the annotations. So
I'll need to find a simple way to strip annotations as part of the inclusion process.

[xogeny]

I think a better approach would be to use the specs.py script in conjunction with the code generation facilities for generating scripts, etc. to create a special package that extends the examples but adds an experiment annotation. This would keep the experiment annotation out of the source code used in the book but still make it easy for tools to test the models.