Add the '.fvtk' for consistency (and to make the example easy to run).
Add the '.fvtk' for consistency (and to make the example easy to run).

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