Merge pull request #84 from ta2yak/patch-1

「Deploy to Heroku」利用時に検索でエラーとなるため手順を追加

README.md

@@ -40,6 +40,7 @@ Using Heroku
 
 1. go to https://heroku.com/deploy
 1. input INSTALL_PLUGINS to install plugins
+1. Upgrade Bonsai ( -> 5.x.x )
 
 Using docker-compose
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