Ruby gem markdown_helper:

• Supports file inclusion for markdown files (which GitHub refuses to do). That means your markdown file can include other files: more markdown, highlighted code, etc.
• Can insert a table of contents into your markdown page.

You don't need to code in Ruby to use markdown_helper. You only need to have Ruby installed, which is the default on many Linux installations.

Type ruby --version. If that succeeds, you already have Ruby installed.

All you need do now is type gem install markdown_helper, and you're ready to use the CLI.

Read all about it on GitHub.