Write Swig templates
Copy Swig views as Nunjucks
Add Swig to Mustache helper
Drop Mustache to avoid complexity

Mustache can't handle raw SassDoc data, nor data indexed with
`sassdoc-indexer`. We need a custom indexer to make it bearable
to Mustache, and we don't want this in the generator for now.

A custom module could be done for this thereafter.
No groups in bare index
Add raw group
Write Jade templates