Discussion: Email validation

Soon, you will need to validate your email to contribute to the discussion.
The main chunk of the work will be done on the Discussion and Identity APIs.
This is just the preliminary work so when it is implemented, we handle it correctly.
It has been tested against a mock.

## Peek
![email-validation](https://f.cloud.github.com/assets/31692/1909682/e484b138-7d04-11e3-93ac-7d24be1e2ae8.png)

![Non shall pass](http://media.giphy.com/media/5MKhiIHdjtYje/giphy.gif)