この問題に関する多くの記事を読みましたが、それでもエラーを解決できませんでした。これは heroku ログの一部です。情報が少ない場合は、red mine のソース コードの他のコードを更新します。
2012-11-05T14:02:54+00:00 app[web.1]: Plugins in vendor/plugins (/app/vendor/plugins) are no longer allowed. Please, put your Redmine plugins in the `plugins` directory at the root of your Redmine directory (/app/plugins)
2012-11-05T14:02:54+00:00 app[web.1]: => Booting WEBrick
2012-11-05T14:02:54+00:00 app[web.1]: => Rails 3.2.8 application starting in production on http://0.0.0.0:40115
2012-11-05T14:02:54+00:00 app[web.1]: => Call with -d to detach
2012-11-05T14:02:54+00:00 app[web.1]: => Ctrl-C to shutdown server
2012-11-05T14:02:54+00:00 app[web.1]: Exiting
2012-11-05T14:02:55+00:00 heroku[web.1]: Process exited with status 1
2012-11-05T14:02:55+00:00 heroku[web.1]: State changed from starting to crashed
2012-11-05T14:02:56+00:00 heroku[router]: Error H10 (App crashed) -> GET ceciits.herokuapp.com/ dyno= queue= wait= service= status=503 bytes=
2012-11-05T14:06:04+00:00 heroku[web.1]: State changed from crashed to down
2012-11-05T14:06:04+00:00 heroku[web.1]: Unidling
2012-11-05T14:06:04+00:00 heroku[web.1]: State changed from down to starting
2012-11-05T14:06:07+00:00 heroku[web.1]: Starting process with command `bundle exec rails server -p 3103`
2012-11-05T14:06:12+00:00 app[web.1]: Plugins in vendor/plugins (/app/vendor/plugins) are no longer allowed. Please, put your Redmine plugins in the `plugins` directory at the root of your Redmine directory (/app/plugins)
2012-11-05T14:06:12+00:00 app[web.1]: => Booting WEBrick
2012-11-05T14:06:12+00:00 app[web.1]: => Rails 3.2.8 application starting in production on http://0.0.0.0:3103
2012-11-05T14:06:12+00:00 app[web.1]: => Call with -d to detach
2012-11-05T14:06:12+00:00 app[web.1]: => Ctrl -C to shutdown server
2012-11-05T14:06:12+00:00 app[web.1]: Exiting
2012-11-05T14:06:13+00:00 heroku[web.1]: Process exited with status 1
2012-11-05T14:06:13+00:00 heroku[web.1]: State changed from starting to crashed
リードアプリが実際にクラッシュした理由がどこにあるのかわかりません。答えてくれてありがとう...