Revert "added social login"

This reverts commit 4b1211159b459e04741e0f78956c74b05040f292.

Conflicts:
	Gemfile
	Gemfile.lock
	Gemfile~
	app/controllers/application_controller.rb~
	app/controllers/sessions_controller.rb~
	app/helpers/sessions_helper.rb~
	app/models/user.rb~
	app/views/layouts/_navbar.html.erb
	app/views/layouts/_navbar.html.erb~
	app/views/layouts/application.html.erb
	app/views/layouts/application.html.erb~
	app/views/sessions/new.html.erb
	app/views/sessions/new.html.erb~
	config/routes.rb
	config/routes.rb~
	db/schema.rb