Add survey sharing UI

Adds a UI for sharing a survey with other registered users. 

Prashant: this is ready for review but shouldn't be merged until the API is also ready. 

![2014-05-06 10 26 26 am](https://cloud.githubusercontent.com/assets/86435/2890626/797d11e0-d52a-11e3-8b5e-b1f8ca242078.png)