Use node-glob to properly cross-platform expand globbing syntax

[airtonix]

the library you're using to expand input files doesn't do anything smart with globbing syntax.

so the following use cases with either not match files or miss out deeply nested directories:

• styledown config.md src/styles/**/*{-*,}.scss > ./dist/styleguide.html
• styledown config.md **/*.scss > ./dist/styleguide.html

Suggest you wrap your argv._ with node-glob to more effectively expand globbing.