considering non-modified attributes as modified when object retrieved as a part of collection

[sashazykov]

It tries to save non-modified attributes when send_only_modified_attributes is true:

[1] pry(main)> drivers = Driver.where('filter[user_id]' => 1)
=> #<Her::Model::Relation:0x007fc4f5a8ed48 @_fetch=nil, @params={"filter[user_id]"=>1}, @parent=Driver>
[2] pry(main)> d = drivers.first
=> #<Driver(drivers/40) created_at="2015-01-18T11:28:14.944Z" updated_at="2016-05-06T07:21:12.443Z" phone="+39393939" user_id=1 id="40">
[3] pry(main)> d.phone = "+7777"
=> "+7777"
[5] pry(main)> d.changes
=> {"created_at"=>[nil, "2015-01-18T11:28:14.944Z"], "updated_at"=>[nil, "2016-05-06T07:21:12.443Z"], "phone"=>[nil, "+7777"], "user_id"=>[nil, 1]}
[6] pry(main)> d.save
=> false
[7] pry(main)> d.response_errors
=> [{:title=>"Param not allowed", :detail=>"created_at is not allowed.", :id=>nil, :href=>nil, :code=>105, :source=>nil, :links=>nil, :status=>"400", :meta=>nil},
 {:title=>"Param not allowed", :detail=>"updated_at is not allowed.", :id=>nil, :href=>nil, :code=>105, :source=>nil, :links=>nil, :status=>"400", :meta=>nil}]

[zacharywelch]

Fixed by #298

Thanks!