Fix os dependant paths in fetcher.
Fix os dependant paths in fetcher.

villalonreina/dipy,beni55/dipy,Messaoud-Boudjada/dipy,oesteban/dipy,sinkpoint/dipy,FrancoisRheaultUS/dipy,beni55/dipy,Messaoud-Boudjada/dipy,oesteban/dipy,sinkpoint/dipy,jyeatman/dipy,samuelstjean/dipy,jyeatman/dipy,matthieudumont/dipy,FrancoisRheaultUS/dipy,nilgoyyou/dipy,rfdougherty/dipy,mdesco/dipy,StongeEtienne/dipy,demianw/dipy,demianw/dipy,matthieudumont/dipy,JohnGriffiths/dipy,JohnGriffiths/dipy,villalonreina/dipy,StongeEtienne/dipy,nilgoyyou/dipy,samuelstjean/dipy,samuelstjean/dipy,rfdougherty/dipy,mdesco/dipy