Feature/language modal

I think it makes more sense for the language selection dropdown to be located under the user dropdown (with "logout" and "change password") rather in the main navigation.

I created a new modal window to house the language selection.

![image](https://cloud.githubusercontent.com/assets/1809908/5429799/f0591348-83c8-11e4-85a9-f30a12f59d3c.png)