README.txt: minor updates suggested by mnestic
README.txt: minor updates suggested by mnestic

bjourne/factor,AlexIljin/factor,bpollack/factor,AlexIljin/factor,bjourne/factor,factor/factor,dch/factor,bpollack/factor,slavapestov/factor,nicolas-p/factor,dch/factor,bjourne/factor,bpollack/factor,slavapestov/factor,sarvex/factor-lang,nicolas-p/factor,sarvex/factor-lang,slavapestov/factor,factor/factor,nicolas-p/factor,nicolas-p/factor,tgunr/factor,AlexIljin/factor,bjourne/factor,mrjbq7/factor,factor/factor,sarvex/factor-lang,slavapestov/factor,factor/factor,mrjbq7/factor,dch/factor,bjourne/factor,AlexIljin/factor,nicolas-p/factor,bjourne/factor,slavapestov/factor,tgunr/factor,AlexIljin/factor,AlexIljin/factor,bpollack/factor,sarvex/factor-lang,dch/factor,sarvex/factor-lang,tgunr/factor,tgunr/factor,mrjbq7/factor,dch/factor,tgunr/factor,sarvex/factor-lang,dch/factor,mrjbq7/factor,bjourne/factor,nicolas-p/factor,slavapestov/factor,bpollack/factor,bpollack/factor,factor/factor,tgunr/factor,mrjbq7/factor,mrjbq7/factor,AlexIljin/factor,sarvex/factor-lang,slavapestov/factor,bpollack/factor,factor/factor,nicolas-p/factor