http://www.noobslab.com/2015/04/tweaksthings-to-do-after-install-of.html
No more minimize/maximize buttons in Nautilus
gsettings set org.gnome.desktop.wm.preferences button-layout ":minimize,maximize,close"
Source : http://askubuntu.com/questions/651347/how-to-bring-back-minimize-and-maximize-buttons-in-gnome-3