def css_compressor # :nodoc:
      case config.css_compressor
      when Crush::Engine
        config.css_compressor
      when Symbol, String
        CSS_COMPRESSORS[config.css_compressor.to_sym]
      else
        Crush.register_css
        Tilt['css']
      end
    end
def css_compressor # :nodoc:
      case config.css_compressor
      when Crush::Engine
        config.css_compressor
      when Symbol, String
        CSS_COMPRESSORS[config.css_compressor.to_sym]
      else
        Crush.register_css
        Tilt['css']
      end
    end
Returns the CSS compression engine, based on
 what's set in `config.css_compressor`. If `config.css_compressor`
 is nil, let Tilt + Crush decide which one to use.