fixed models loading in "rake sunspot:reindex"

rake sunspot:reindex does not work in production environment if you include namespaced modules in your models:

```
$ RAILS_ENV=production rake sunspot:reindex --trace
** Invoke sunspot:reindex (first_time)
** Invoke environment (first_time)
** Execute environment
** Execute sunspot:reindex
rake aborted!
Expected /path/to/project/releases/20120317160302/app/models/ontology/import.rb to define Ontology::Import
```

Content of `app/models/ontology/import.rb`:

```
module Ontology::Import
  extend ActiveSupport::Concern
end
```

Content of `app/models/ontology.rb`:

```
class Ontology < ActiveRecord::Base
  include Ontology::Import
end
```