Niftier summation of total order price

Hi, Ivar and whom it may concern

My name is Jonas Amundsen and I'm one of Iteras summer interns for 2013. Tommy said that you were fiddling with some cool technologies and mentioned this project, so I figured I would check it out.

I have been messing around with Ruby and particularly Ruby on Rails for the last three years and I am really beginning to know my way around it. I would love to give you feedback and contribute a bit to the project, to show you guys what I can do.

This is a really small commit and the purpose of the pull request is really just to test the waters and see what kind of contributions you accept from outsiders. Is there any other channel of communication for this project? IRC channel perhaps?

By utilizing built in methods in Ruby and the Rails framework itself, one can sum the price of an order in a way that is in my opinion sweeter, neater and more mind-boggling. Also, it reduces the line count by a total of 6!