Should support stripping of 'humanized' attribute

If I have the following:

``` ruby
autocomplete_for :project, :code do
  self.project = self.site.projects.find_by_code @project_code.strip!
end
```

I need to explicitly strip @project_code in order to prevent incorrect matches due to extraneous whitespace.  Would be more DRY if the generated instance variable was stripped when initialized.  
