bogn/mm-sluggable — pull request #1 by codegourmet (2013-03-21 12:08:15+00:00)
Title: used self.send instead of direct mongo accessor

needed when mirroring an attribute from the nested model into the document.
example:

```ruby
class Outer
include MongoMapper::Document
one :inner
sluggable :title

def title
inner.title
end
end
```