Updates NestedAttributes Module to fix Update Composite Key Parsing Bug

I noticed recently an error with updating nested attributes for an app I'm working on. After some examination I discovered that the code in the NestedAttributes Module is not correctly parsing id's from the attributes_collection for composite keys. These code change makes modification's in two locations in the assign_nested_attributes_for_collection_association method to ensure association's proxy_target correctly matches records with the attributes['id'] parameter value for both standard and composite primary keys, allowing for nested updates to occur.