Removing this line causes:

```
/home/travis/build/amatsuda/kaminari/spec/models/active_record/scopes_spec.rb:14:in `<top (required)>': uninitialized constant Kaminari::ActiveRecordExtension (NameError)
	from /home/travis/.rvm/gems/ruby-1.9.3-p448/gems/rspec-core-2.14.5/lib/rspec/core/configuration.rb:896:in `block in load_spec_files'
	from /home/travis/.rvm/gems/ruby-1.9.3-p448/gems/rspec-core-2.14.5/lib/rspec/core/configuration.rb:896:in `each'
	from /home/travis/.rvm/gems/ruby-1.9.3-p448/gems/rspec-core-2.14.5/lib/rspec/core/configuration.rb:896:in `load_spec_files'
	from /home/travis/.rvm/gems/ruby-1.9.3-p448/gems/rspec-core-2.14.5/lib/rspec/core/command_line.rb:22:in `run'
	from /home/travis/.rvm/gems/ruby-1.9.3-p448/gems/rspec-core-2.14.5/lib/rspec/core/runner.rb:80:in `run'
	from /home/travis/.rvm/gems/ruby-1.9.3-p448/gems/rspec-core-2.14.5/lib/rspec/core/runner.rb:17:in `block in autorun'
```