Don't eagerly load associations with :order

```
  1) EagerRecord has_many :through associations with :order should not generate invalid query
     Failure/Error: User.all.flat_map(&:groups).should == Group.all.first
     ActiveRecord::StatementInvalid:
       SQLite3::SQLException: no such column: groups.active_at: SELECT "groupings".* FROM "groupings" WHERE ("groupings".user_id IN (105,106,107,108,109,110,111,112))  ORDER BY groups.active_at DESC, groups.id DESC
     # ./lib/eager_record/eager_preloading.rb:21:in `find_by_sql_with_eager_preloading'
     # ./lib/eager_record/eager_preloading.rb:76:in `load_target_with_eager_preloading'
     # ./spec/examples/eager_record_spec.rb:146:in `each'
     # ./spec/examples/eager_record_spec.rb:146:in `flat_map'
     # ./spec/examples/eager_record_spec.rb:146:in `block (3 levels) in <top (required)>'
```