See static-src/README.rst for details about how it works.

Python-commonmark is deprecated, and recommends markdown-it-py instead.

This commit also introduces an abstract muppet.markdown module to allow
easier switching in the future, and enables id's for all headers in the
generated HTML.

This also allows sphinx to actually find these declarations.

Documentation can now be generated to HTML through sphinx.
Some docstrings have been updated to be on the correct format.

- Moved most datatypes to own modules
- changed output to take a generator instance for multiple output forms
- Wrote tests for the "parser"
- fixed some bugs revealed in the parser while writing those tests.