temp workaround for sass/node-sass#425
temp workaround for sass/node-sass#425

only `sourceMap: true` works

vovkasm/grunt-sass,xzyfer/grunt-sass,mmcev106/grunt-sass,kaij/grunt-sass,58bits/grunt-sass-revisited,fbiz/grunt-sass,justame/grunt-sass,vladikoff/grunt-sass,am11/grunt-sass,sindresorhus/grunt-sass