Thanks for the help. Now I can continue following the book.
This was done on MS Windows.
I rolled back migration (rails console)
deleted plugin with windows explorer in directory "(..)shovell/vendor/plugins" acts_as_taggable_on_steroids ('Cause otherwise rails tracked plugin location, renaming folder didn't work)
deleted migration file with windows explorer in directory "(..)shovell/db/migrate/(##)actsas_taggable_migration.rb"
installed Git as instructed in articles
executed command (below) in shovel application to get plugin the new way
git clone http://github.com/jviney/acts_as_taggable_on_steroids.git
executed migration steps from the book
ruby script/generate acts_as_taggable_migration
and everything is working. What a satisfaction! :eye: