chore(docs): downloads - promote npm
chore(docs): downloads - promote npm

In the download modal on the demo page, changed Bower info
to suggest using npm instead.

Closes #4734

infowrap/bootstrap,christor/bootstrap,benhalverson/bootstrap,angular-ui/bootstrap,deeg/bootstrap,Foxandxss/bootstrap,benhalverson/bootstrap,angular-ui/bootstrap,icfantv/bootstrap,pdsoftplan/bootstrap,christor/bootstrap,burlhock/bootstrap,icfantv/bootstrap,fpipita/bootstrap,shiftagent/ui-bootstrap,BookingBug/bootstrap,deeg/bootstrap,byronigoe/bootstrap,matteopic/bootstrap,Lincoln-xzc/angular-ui-bootstrap,justin-john/bootstrap-1,wesleycho/bootstrap,292388900/bootstrap,Kpler/bootstrap,connyay/bootstrap,davious/angular-ui-bootstrap,caoruiy/bootstrap,Foxandxss/bootstrap,byronigoe/bootstrap,shiftagent/ui-bootstrap,benhalverson/bootstrap,Servoy/bootstrap,justin-john/bootstrap-1,connyay/bootstrap,BookingBug/bootstrap,292388900/bootstrap,benhalverson/bootstrap,vfiles/bootstrap,pdsoftplan/bootstrap,looker/bootstrap,burlhock/bootstrap,infowrap/bootstrap,looker/bootstrap,Servoy/bootstrap,Kpler/bootstrap,wesleycho/bootstrap,Lincoln-xzc/angular-ui-bootstrap,davious/angular-ui-bootstrap,fpipita/bootstrap,mabi/bootstrap,shootermv/bootstrap,mabi/bootstrap,RobJacobs/bootstrap,caoruiy/bootstrap,matteopic/bootstrap,shootermv/bootstrap,vfiles/bootstrap,RobJacobs/bootstrap