Add right click logo modal window

Now, when a user attempts to use the logo from the website, we give them the option to use one of our high res versions instead. This can be improved as we develop the branding guidelines more.

This is what it looks like:

![open data institute](https://f.cloud.github.com/assets/109774/1446150/7ebe27b0-4232-11e3-91c4-4baee335570a.png)