io.streams.sequence: support slices (fix io.streams.peek test failure).
io.streams.sequence: support slices (fix io.streams.peek test failure).

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