add mkt-prompt element

- Need to work on mobile/tablet

![screen shot 2014-12-18 at 6 05 00 pm](https://cloud.githubusercontent.com/assets/674727/5499226/7038bf22-86e0-11e4-9834-51fe33050cce.png)

@mstriemer @spasovski 
i want to abstract that logic into the component so I don't have to write that listener everywhere. I don't plan on this expanding to be a do-it-all modal. Just want it to handle the common cases where you have a cancel and submit, which is most cases (add review, report abuse, give feedback).