update readme to move away from jquery plugins repo and towards npm
update readme to move away from jquery plugins repo and towards npm

bgrins/spectrum,kotmatpockuh/spectrum,GerHobbelt/spectrum,liitii/spectrum,ajssd/spectrum,safareli/spectrum,armanforghani/spectrum,ajssd/spectrum,ginlime/spectrum,ginlime/spectrum,maurojs25/spectrum,maurojs25/spectrum,armanforghani/spectrum,shawinder/spectrum,kotmatpockuh/spectrum,GerHobbelt/spectrum,bgrins/spectrum,safareli/spectrum,shawinder/spectrum,liitii/spectrum