DOC: expanding release notes for OSX and windows
DOC: expanding release notes for OSX and windows

Instructions for the mpkg builds in particular.

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