DOC: Another small change in documentation as suggsted by @arokem
DOC: Another small change in documentation as suggsted by @arokem

FrancoisRheaultUS/dipy,jyeatman/dipy,nilgoyyou/dipy,oesteban/dipy,demianw/dipy,nilgoyyou/dipy,StongeEtienne/dipy,villalonreina/dipy,StongeEtienne/dipy,jyeatman/dipy,sinkpoint/dipy,demianw/dipy,JohnGriffiths/dipy,sinkpoint/dipy,matthieudumont/dipy,matthieudumont/dipy,oesteban/dipy,FrancoisRheaultUS/dipy,villalonreina/dipy,JohnGriffiths/dipy