jnunemaker/mongomapper — pull request #447 by darragh (2012-09-07 13:23:29+00:00)
Title: partial records incorrectly added to IdentityMap when using Plucky::Query#each

Here's what I noticed

```ruby
> MongoMapper::Plugins::IdentityMap.repository.clear
=> {}
> Tag.where(:app_id => 6).order(:name.asc).only(:id, :name).each {|_|}
=> 6} @cursor_id=>
> MongoMapper::Plugins::IdentityMap.repository.count
=> 51
```

subsequent queries for complete tags would only return the partial records loaded from the identity map.

This behaves differently to using #all.