Fix regression in bundler support
Fix regression in bundler support

Commit 35ad9cd45e73 introduced a regression that breaks bundler support. This occurs because rather than spawning `bundle exec sass ...` it would now spawn `sass bundle exec ...`.
konder/grunt-contrib-sass,kentendo/grunt-contrib-sass,liquidmetal/grunt-contrib-sass,cvrebert/grunt-contrib-sass,gruntjs/grunt-contrib-sass,cvrebert/grunt-contrib-sass,craigweston/grunt-contrib-sass,linemanjs/grunt-contrib-sass,freeyiyi1993/grunt-contrib-sass