attr_searchable, the gem to add database agnostic fulltext search to ActiveRecord (for Mysql and PostgreSQL) is a young and ambitious project. As its set of features grew, it has become neccessary to change its DSL and name. Thus, 'attr_searchable' is called 'search_cop' now.
In addition to the new name, search_cop v1.0.0 is out now and ships with search_scope's:
Check it out and install or migrate to 'search_cop'