Verto

Fixes:

- Verto container tags, are now supported in markdown lists.

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Fixes:

- Verto tags and custom tags, are now support embedding into markdown lists.

Fixes:

- A new more descriptive error when an argument is given and not readable.
- Custom HTML string parsing has been implemented, allowing for correct parsing of HTML and XHTML in templates.

Documentation:

- Basic example in README.
- New contributing documentation.
- Fixed reference to incorrect file in the image processor documentation.
- Added new documentation for implicit processors.

Fixes:

- pypi configuration fixes.
- pyup configuration to use develop branch.
- Improved asset file loading for deployed package.

Fourth prerelease of the Verto converter.
(The project was renamed to Verto from Kordac in release.)

Adds support for the following processors:

- `iframe`
- `interactive`
- `heading`
- `scratch`
- `table-of-contents`

Features:

- The `scratch` processor supports `split` and `random` options.

Fixes:

- Scratch blocks work with other extensions.
- Glossary slugs are now added to the output of Verto.
- Processors are now ordered correctly.

Fixes:

- Updated documentation and changelog.