Use the initalization phase to install all of the Python versions
and run the tests on startup, making subsequent test runs faster.

Signed-off-by: Mike Fiedler <[email protected]>

* test: add test fixtures for admonitions

Create failing examples to test desired behavior.

Signed-off-by: Mike Fiedler <[email protected]>

* feat: allow `class` attributes for `div` and `p`

docutils' admonitions renders the blocks using `class` attributes,
which can then be styled via CSS.
Allow `class` attributes to pass through the cleaner.

Signed-off-by: Mike Fiedler <[email protected]>

* fix: add `class` to existing test fixtures

With the allowance that `class` may now be passed for `div`,
update fixtures to conform to the new directive.

Signed-off-by: Mike Fiedler <[email protected]>

Co-authored-by: Dustin Ingram <[email protected]>

Signed-off-by: Mike Fiedler <[email protected]>

Previously exlcuded directives made for incorrect rendering of rst table
cells spanning more than a single column or row.

Fixes #182

Signed-off-by: Mike Fiedler <[email protected]>

* chore: update codebase for modern python

We're on Python 3.7 and higher, so we can clean up any artifacts left
from previously-supported Python eras.

Most of the heavy lifting was done with `pyupgrade` followed by unused
improts removal (thanks to `flake8` check)

Refs: https://pypi.org/project/pyupgrade/

Closes #203

Signed-off-by: Mike Fiedler <[email protected]>

* refactor: replace `os.path`/`glob` with `pathlib`

Since Python 3.4, `pathlib` provides a nicer interface to manipulate
paths, removing the need to split and reassemble strings.

The addition of `pytest.param(..., id=fn.name)` is to set the test name
output to a human-friendly string in the event of failure or `--verbose`

Signed-off-by: Mike Fiedler <[email protected]>

* chore: replace deprecated setuptools entry

As of setuptools v56.0.0, the `license_file` entry is deprecated,
raising `SetuptoolsDeprecationWarning` during the `packaging` step.

Refs: pypa/setuptools#2620

Signed-off-by: Mike Fiedler <[email protected]>

The first step to allowing math directives to be rendered on PyPI is
to enable the directive's warning to pass.

`docutils` tells us to pass a path to the `math_output` setting.
Since we `clean` the output, we can pass anything we want, as control
of the CSS will be handed on PyPI.

Refs: https://docutils.sourceforge.io/docs/user/config.html#math-output

This does **not** solve for Markdown math.

Resolves #115
Resolves #172

Signed-off-by: Mike Fiedler <[email protected]>

* test: add failing test for language attribute

Signed-off-by: Mike Fiedler <[email protected]>

* feat: preserve lang attribute in markdown

In order to allow the `lang` attribute on `pre` code blocks, add it to
the post-syntax highlighting step, and then allow through the sanitizer.

Signed-off-by: Mike Fiedler <[email protected]>

* test: update tests to include preserved `lang`

Signed-off-by: Mike Fiedler <[email protected]>

Co-authored-by: Dustin Ingram <[email protected]>

Signed-off-by: Mike Fiedler <[email protected]>