Added documentation about Sass setup.
Added documentation about Sass setup.

akikoo/grunt-frontend-workflow,Brother-Simon/grunt-frontend-workflow,Brother-Simon/grunt-frontend-workflow,akikoo/grunt-frontend-workflow,Brother-Simon/grunt-frontend-workflow,akikoo/grunt-frontend-workflow,Brother-Simon/grunt-frontend-workflow,akikoo/grunt-frontend-workflow,akikoo/grunt-frontend-workflow,akikoo/grunt-frontend-workflow,Brother-Simon/grunt-frontend-workflow,Brother-Simon/grunt-frontend-workflow