Add link to PHPUGHH on Meetup to footer

Adding link to list at the bottom temporarily using the twitter icon
Add link to PHPUGHH on Meetup to footer

Add meetup icon, taken from meetup.com.
Doesn't have the right size.
Add link to PHPUGHH on Meetup to foote

Meetup icon with proper dimensions
Add link to PHPUGHH on Meetup to footer

Adding meetup icon to sprite sheet
Add link to PHPUGHH on Meetup to footer

Adding CSS to display correct icon
Add link to PHPUGHH on Meetup to footer

Ran sprites.png through png crunch, shaved off ~2KB
Merge pull request #40 from kiltec/issue_38

Add link to PHPUGHH on Meetup to footer