doc: improved documentation and fixed PEP8
doc: improved documentation and fixed PEP8

JohnGriffiths/nipype,mick-d/nipype_source,glatard/nipype,Leoniela/nipype,Leoniela/nipype,gerddie/nipype,arokem/nipype,dgellis90/nipype,iglpdc/nipype,glatard/nipype,wanderine/nipype,mick-d/nipype_source,pearsonlab/nipype,pearsonlab/nipype,fprados/nipype,sgiavasis/nipype,rameshvs/nipype,FCP-INDI/nipype,dgellis90/nipype,FCP-INDI/nipype,JohnGriffiths/nipype,mick-d/nipype,blakedewey/nipype,dgellis90/nipype,wanderine/nipype,FredLoney/nipype,carolFrohlich/nipype,FredLoney/nipype,dgellis90/nipype,gerddie/nipype,wanderine/nipype,arokem/nipype,carolFrohlich/nipype,dmordom/nipype,JohnGriffiths/nipype,fprados/nipype,FCP-INDI/nipype,carlohamalainen/nipype,JohnGriffiths/nipype,sgiavasis/nipype,carolFrohlich/nipype,pearsonlab/nipype,grlee77/nipype,fprados/nipype,pearsonlab/nipype,rameshvs/nipype,glatard/nipype,grlee77/nipype,carlohamalainen/nipype,FCP-INDI/nipype,arokem/nipype,iglpdc/nipype,rameshvs/nipype,blakedewey/nipype,Leoniela/nipype,gerddie/nipype,carolFrohlich/nipype,dmordom/nipype,iglpdc/nipype,rameshvs/nipype,sgiavasis/nipype,mick-d/nipype,grlee77/nipype,grlee77/nipype,mick-d/nipype_source,blakedewey/nipype,gerddie/nipype,dmordom/nipype,mick-d/nipype,carlohamalainen/nipype,glatard/nipype,wanderine/nipype,FredLoney/nipype,blakedewey/nipype,iglpdc/nipype,mick-d/nipype,sgiavasis/nipype,arokem/nipype