[Sass] Allow chained @extends.
[Sass] Allow chained @extends.

dylannnn/sass,macressler/haml,Anshdesire/sass,ridixcr/sass,xzyfer/sass,hcatlin/sass,MetaAshley/sass,srawlins/sass,OrenBochman/sass,zaru/sass,tangposmarvin/sass,chriseppstein/haml,StephanieMak/sass,danielfein/sass,schneems/sass,nickg33/sass,nicklima/sass,jaroot32/sass,sideci-sample/sideci-sample-haml,baiyanghese/sass,Anshdesire/sass,uniba/hamldoc_ja,stewx/sass,liquidmetal/sass,keithpitty/haml,antonifs/sass,briangonzalez/sass,PMArtz92/sass,askl56/sass,xzyfer/sass,jaroot32/sass,DanteKaris/sass,HugoRLopes/sass,rammy7219/sass,concord-consortium/haml,lmetla/sass,stewx/sass,hcatlin/sass,Nzaga/sass,cmpereirasi/sass,Ahnita/sass,nazar-pc/haml,Iamronan/sass,MetaAshley/sass,antonifs/sass,tangposmarvin/haml,stanhu/haml,dg1dd1ngs/haml,amitsuroliya/sass,amatsuda/haml,oss-practice/sass,JuanitoFatas/sass,PMArtz92/sass,cmpereirasi/sass,Galactix/sass,tangposmarvin/sass,StephanieMak/sass,modulexcite/sass,Ahnita/sass,askl56/sass,dg1dd1ngs/haml,nickg33/sass,Andrey-Pavlov/sass,Industrys/sass,Iamronan/sass,nicklima/sass,tenderlove/sass,srawlins/sass,ridixcr/sass,DanteKaris/sass,saper/sass,Nzaga/sass,saper/sass,liquidmetal/sass,chriseppstein/haml,stanhu/haml,amitsuroliya/sass,macressler/haml,dylannnn/sass,haml/haml,zaru/sass,Andrey-Pavlov/sass,srinivashappy/sass,danielfein/sass,keithpitty/haml,rammy7219/sass,OrenBochman/sass,HugoRLopes/sass,nazar-pc/haml,lmetla/sass,JuanitoFatas/sass,tangposmarvin/haml,14113/sass,srinivashappy/sass,haml/haml,haml/haml,modulexcite/sass,schneems/sass,Galactix/sass,haml/haml,Industrys/sass,chriseppstein/sass