Fixed the issue with missing 'payment' method in _order_details.html.erb.

The issue was related to the fact that "payment" method has been replaced with "paymentS". So now there is a partial that visualizes each payment. I created exact match of this file and put there a <% elsif source.is_a? Spree::PaypalAccount %> check to put the paypal info if paypal payment is detected.

Related to issue #151