Adds a new option, `--no-markdown-toc`, to turn off Table of Contents generation. Table of contents are now generated by default with markdown output, including through the `readme` command.
Fixes https://github.com/documentationjs/documentation/issues/220
Note that the AST now carries the name “mdast”, meaning
utilities (such as mdast-util-inject) keep their name.
This name-change includes the `mdast` formatter, which also changed
to `remark`.
Additionally:
* Update relating packages.
* Fix a bug where `text` nodes without value were
[generated](6b905aefb1/lib/output/markdown_ast.js (L144)).
* Compare strings as lowercase, to permit for v4+ compatibility
* Fix bad reference to loc.name
* Update README badge and fixture
* Remove brfs dependency
* Remove traverse
* Remove browser transform support