updated CircleCI badge to use master
updated CircleCI badge to use master

zhaar/BrightFutures,Thomvis/BrightFutures,morizotter/BrightFutures,zhaar/BrightFutures,zenkimoto/BrightFutures,hoanganh6491/BrightFutures,Thomvis/BrightFutures,tranhieutt/BrightFutures,Noobish1/BrightFutures,MattesGroeger/BrightFutures,MattesGroeger/BrightFutures,hoanganh6491/BrightFutures,Noobish1/BrightFutures,tranhieutt/BrightFutures,zenkimoto/BrightFutures,morizotter/BrightFutures