enhc The donate form with button UI

Uses a new version of the button class to make square buttons to create
this interface. Still works as a form of radio buttons.

TODO
- Clicking on the custom amount input box will not trigger the radio
option, may need JS to help with this.

@ericronne as you can see, I have not been messing with the fonts at this point because they are not finalized.


When selecting first payment amount:
![screen shot 2014-11-12 at 2 46 12 pm](https://cloud.githubusercontent.com/assets/1701077/5020133/c8227f16-6a7a-11e4-9a5d-98045cf029df.png)

When entering custom amount:
![screen shot 2014-11-12 at 2 46 21 pm](https://cloud.githubusercontent.com/assets/1701077/5020130/c3d72d8a-6a7a-11e4-9bc9-fe37d0973b14.png)

When at small breakpoint:
![screen shot 2014-11-12 at 2 46 39 pm](https://cloud.githubusercontent.com/assets/1701077/5020139/cdc1db10-6a7a-11e4-8783-11ed8dd46d34.png)


Note to self: pay attention to generated css.