Support editing responses

Lets logged-in users edit responses. 

![screen shot 2014-11-21 at 1 01 23 pm](https://cloud.githubusercontent.com/assets/86435/5146835/9bccad1e-717e-11e4-8f82-4da78c482657.png)

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![screen shot 2014-11-21 at 1 01 28 pm](https://cloud.githubusercontent.com/assets/86435/5146836/9dc3406a-717e-11e4-84ab-0dcf94af6c7c.png)

Currently uses native form styling.  I experiment with [customSelect](http://adam.co/lab/jquery/customselect/) but wasn't able to come up with a style that preserved elements of the layout and looked intuitive. I'd still like to use native styling, but I don't think it should block the functionality. 

Also fixes an overflow problem by switching clearfix method.