Access Code modal

Fix #1186 

Here's a modal that asks for the access code. We should also include some information on here on either: 1) how to get started on a project or 2) how Leada works to help people get hired.

The user only ever sees this modal once. Thoughts, @brianliou @tristantao 

![screen shot 2014-10-07 at 1 00 52 pm](https://cloud.githubusercontent.com/assets/1435378/4549286/d59e8926-4e5c-11e4-9941-e22548a58317.png)