add meetup logo and fix some responsive design bugs

- Add meetup logo (image), since it doesn't exist in the fontawesome package.
- Fix a design bug when viewing the site with mobile, the social media floats from the sidebar.

 and like they said, an image is worth a thousand words :

![screenshot from 2014-09-22 13 23 54](https://cloud.githubusercontent.com/assets/3820376/4356006/1f22d3b4-4254-11e4-8afd-ea305fb6db20.png)