User can categorize posts

https://trello.com/c/WlRza0am/8-as-a-user-i-can-categorize-a-post-as-being-bikes-boats-etc

![screen shot 2014-11-06 at 11 33 32 am](https://cloud.githubusercontent.com/assets/8681076/4939403/b8dc3dc8-65d2-11e4-845f-4505f379ece4.png)

This branch also includes some error correction from a previous merge issue
Could we redirect to a more specific path like above - redirect_to @post.area?