v6.0.0

Theo v6 is a complete re-write that allowed us to fix some long standing issues and separate the core engine from the Gulp plugin.

• Handlebars support for registerFormat() (@kaelig)
• Formats can now receive additional options
• Added new formats
  • cssmodules.css (@nickbalestra)
  • custom-properties.css
  • module.js
• CLI support (@nickbalestra @tomger)
• Array support for "props" (as long as each prop has a "name" key) which will preserve prop order in the final output
• Bug fixes and documentation for several existing formats (@corygibbons @dennisreimann @micahwood @didoo)

Big thanks to @kaelig for helping kickstart this release and to all the alpha/beta testers who reported issues and fixed bugs!

⚠️ Breaking changes

• Aliases are only available to files that directly import them – see #101
• The Gulp plugin is in a separate gulp-theo package
• Renamed the .meta key to meta
• Removed the includeRawValue option in favor of always adding an originalValue key in each transformed prop