replaces ogp images with geoblacklight icon font

Will be useful for scaling icons and fonts moving forward. Also allows customization at institutions for branding.

Icon font generated using FontCustom here: https://github.com/geoblacklight/geoblacklight-icons

![screen shot 2014-11-06 at 11 11 08 pm](https://cloud.githubusercontent.com/assets/1656824/4948379/3948e98e-660a-11e4-9e45-50c5c32ac8ba.png)