Users can see top bids and submit bids to a post

![image](https://cloud.githubusercontent.com/assets/8669803/4995470/18cdb83c-698f-11e4-8675-300a29a09a86.png)

![image](https://cloud.githubusercontent.com/assets/8669803/4995474/20827d74-698f-11e4-9329-6ce020294cc6.png)


CAN I GET A BAM?
Actually - all the other models (like [Comment](https://github.com/ncliffor/biddr/blob/master/app/models/comment.rb)) have the associations before the validations, so I'd switch this up.