Sass improvements

[gpakosz]

This PR adds further improvements to the :sass and :sass_sourcemap filters.

Detailed description

• :sass and :sass_sourcemap filters now require the :css_path option, which produces source maps where the optional "file" field has a correct value
• the :sass filter now supports the generation of inline, base 64 encoded, source maps

• Tests
• Documentation

Related issues

nanoc/nanoc.app#227

[denisdefreyne]

Requiring the :css_path option will be a backwards-incompatible change. Is there a way to have a default?

[gpakosz]

It's indeed backward incompatible but it's the way it should have been in the first place 😢

[gpakosz]

Well I'll think about it, maybe I can do the following: if css_path is not given, use a dummy one then remove it from the generated sourcemap instead of letting incorrect information go through

[denisdefreyne]

Alternatively, require css_path to be given only if sourcemap_path is set to :inline. What do you think?

[gpakosz]

In fact it has nothing to do with inline source maps. It's just Sass won't let you omit the optional "file" entry in the output source map. So the conservative strategy would be to give Sass a dummy value then change that after the source map has been produced

[gpakosz]

There, now css_path is optional