Update for running with rails 4.1.0

The  where_values_hash method gained an optional parameter. This needs the
monkey patched version to be updated for compatibility to the Rails 4.1.0 stable.

Maybe related to: #244


All test running fine. With this fix the association, ```Post.first.comments << Comment.first``` on ```has_many_through``` which was broken before, also works fine.  But I'm not 100% sure if it is the right way for fixing this. Feel free to comment or pull.