Add support for embedding Open Graph and Twitter pages

The new Mojolicious-Plugin-LinkEmbedder support fetching open graph information. This pull request adds the following styling:

![screenshot from 2014-10-12 20 01 02](https://cloud.githubusercontent.com/assets/45729/4606967/c147d82a-5239-11e4-9da4-afc33090eb90.png)