Fix ActiveResource::Base.build method

@maartenvg 

## Problem

ActiveResource 4 changes the signature of the `new_element_path` method. See https://github.com/rails/activeresource/commit/fd3616a46b90b10015a47b1275c1109ab836e9f3

## Solution

Pass the attributes to `new_element_path` for ActiveResource >= 4.