TST - added test for affine with streamline_mapping
TST - added test for affine with streamline_mapping

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