Add Marketplace controller, Listing Controller, listing show

https://trello.com/b/iqXz1GRa/cycle-the-city-brian

![image](https://cloud.githubusercontent.com/assets/8669803/5078279/6f637c06-6e79-11e4-92c6-17553bf43c48.png)

![image](https://cloud.githubusercontent.com/assets/8669803/5078297/a2f8021c-6e79-11e4-8c68-dfc42dc1fd69.png)

![image](https://cloud.githubusercontent.com/assets/8669803/5078301/aabeac62-6e79-11e4-8545-83ec313a850a.png)


Actually, yes.  Users will be able to filter the area to whatever they like.  Sometimes they need to buy a unique part from across the country