RF: bump minimum numpy version to 1.5
RF: bump minimum numpy version to 1.5

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