fix typo in grouping docs, add more examples
fix typo in grouping docs, add more examples

bpollack/factor,bpollack/factor,bjourne/factor,bjourne/factor,bpollack/factor,bpollack/factor,dharmatech/factor,slavapestov/factor,factor/factor,ehird/factor,bpollack/factor,AlexIljin/factor,littledan/Factor,mcandre/factor,kingcons/factor,ceninan/factor,ceninan/factor,tgunr/factor,mcandre/factor,erg/factor,AlexIljin/factor,ceninan/factor,dharmatech/factor,dch/factor,erg/factor,slavapestov/factor,sarvex/factor-lang,factor/factor,tgunr/factor,seckar/factor,dch/factor,mrjbq7/factor,mcandre/factor,Keyholder/factor,nicolas-p/factor,dch/factor,kingcons/factor,sarvex/factor-lang,factor/factor,AlexIljin/factor,bpollack/factor,slavapestov/factor,erg/factor,AlexIljin/factor,tgunr/factor,factor/factor,seckar/factor,bjourne/factor,erg/factor,mcandre/factor,ceninan/factor,erg/factor,nicolas-p/factor,mrjbq7/factor,mrjbq7/factor,bjourne/factor,tgunr/factor,cataska/factor,AlexIljin/factor,nicolas-p/factor,cataska/factor,erg/factor,cataska/factor,dch/factor,slavapestov/factor,dch/factor,erg/factor,dch/factor,bjourne/factor,dharmatech/factor,bjourne/factor,slavapestov/factor,nicolas-p/factor,tgunr/factor,slavapestov/factor,slavapestov/factor,cataska/factor,mcandre/factor,nicolas-p/factor,sarvex/factor-lang,littledan/Factor,mcandre/factor,littledan/Factor,jwmerrill/factor,mcandre/factor,factor/factor,factor/factor,mrjbq7/factor,seckar/factor,nicolas-p/factor,AlexIljin/factor,ehird/factor,ehird/factor,Keyholder/factor,kingcons/factor,mrjbq7/factor,kingcons/factor,sarvex/factor-lang,Keyholder/factor,sarvex/factor-lang,jwmerrill/factor,mrjbq7/factor,bjourne/factor,AlexIljin/factor,jwmerrill/factor,littledan/Factor,nicolas-p/factor,sarvex/factor-lang,tgunr/factor,bpollack/factor,sarvex/factor-lang