Rails42 update

Rails 4 deprecated  ::ActiveRecord::ConnectionAdapters::Column.value_to_boolean(value) and it was removed in 4.2.0

A pretty solid replacement implementation seems like ::ActiveRecord::Type::Boolean.new.type_cast_from_database(value), though it would probably work just to use !!value

I also updated the dummy file to remove deprecation warnings and added the gems I needed to get the specs running to the gemspec.