Out of date doc for Sass::Plugin::Rack

[bambery]

Sass 3.2.9 (Media Mark)

options= was deprecated, meaning options.merge will fail as given in this example:

https://sass-lang.com/docs/yardoc/Sass/Plugin/Rack.html

Also, though you have to require sass/plugin/rack, use Sass::Plugin::Rack is not strictly necessary to use Sass::Plugin if you are using it just to compile multiple files or folders on a filesystem from sass to css, as one would do for a precompile rake task, and as is suggested in the engine docs:

https://sass-lang.com/docs/yardoc/Sass/Engine.html

The phrasing of the two doc pages seems somewhat contradictory as to what exactly Sass:Plugin can be used for.

[nex3]

I'm moving this issue to the new Ruby Sass repository because it's specific to Ruby Sass's implementation.