updates feedback form cancel button

Fixes #232 

Changes feedback form cancel button from link to button when javascript is enabled. Styles button to look like a link.

Note: @jvine styled button link does not have `border-bottom` because it looked too funky 

![screen shot 2014-07-02 at 3 40 42 pm](https://cloud.githubusercontent.com/assets/1656824/3463456/ee31459c-0239-11e4-8634-e3f5e42e898b.png)

![screen shot 2014-07-02 at 3 41 13 pm](https://cloud.githubusercontent.com/assets/1656824/3463467/fe125550-0239-11e4-80c1-b62602ec0d0f.png)