/script/rails g jquery:install
すると
deprecated You are using Rails 3.1 with the asset pipeline enabled, so this generator is not needed.
The necessary files are already in your asset pipeline.
Just add `//= require jquery` and `//= require jquery_ujs` to your app/assets/javascripts/application.js
If you upgraded your app from Rails 3.0 and still have jquery.js, rails.js, or jquery_ujs.js in your javascripts, be sure to remove them.
If you do not want the asset pipeline enabled, you may turn it off in application.rb and re-run this generator.
よくわからないけど
・app/assets/javascripts/application.js
require jquery require jquery_ujs
これで起動できた
◯もんごいど（※もんごアイディーではない）
mongoid
・Railsの失敗コマンド
rails d controller lalala
rails d model yadayada
rails d scaffold hohoho
