added test for serial execution of all callbacks of a single future
added test for serial execution of all callbacks of a single future

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