FEAT: Include test option for compiling notebooks selective with and without code tests

[mmcky]

Thanks @jlperla for the following:

@arnavs You can take a shot at this. The basic idea is that we would introduce a :class: test as a parallel to :class: solution`

The beautiful thing now is that we can almost use identical code wherever the word solution is used in the https://github.com/QuantEcon/sphinxcontrib-jupyter/pull/72/files

In partiular,

• in sphinxcontrib/jupyter/__init__.py

  app.add_config_value("jupyter_drop_tests", False, "jupyter")

• in sphinxcontrib/jupyter/writers/translate_code.py we need to parse the test class and add a flag in the visitor

  self.test= _parse_class["test"]

  Then in the visitor if we are in a test and the option is set to drop them, we just pass and don't output the code. i.e.

  if self.solution and self.jupyter_drop_solutions:    
          pass

• In tests/conf.py we set the option with jupyter_drop_tests = True or jupyter_drop_solutions = False
• Add tests, of course.

You can ask @mmcky but I think a lot of the other stuff in the PR also does something with output blocks, which I believe is orthogonal?

[arnavs]

@mmcky I think we can close this now.

[mmcky]

thanks @arnavs