First draft
Process theme `index.js` depending on vars
Remove unsupported alias + add Sass usage prompt
Apply system to all template engine + refine
Handlebars not handelbars >_<
- Fix #2
Validate `themeEngine` option + rework prompts logic
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
Added Grunt and Gulp generators, first draft
Stora default config as literal object
Add conditional dependencies
No more `.sassdocrc`
Comment example line with undefined variable
Update Gruntfile template
Comment unused examples