Dynamically add next event to homepage

I thought it'd be cool if the homepage had something more specific/lively about our events, so I've added some code to fetch details about the next meetup and insert that into the homepage.

Meetup.com doesn't allow cross domain requests, so I had to create a [key-signed request](http://www.meetup.com/meetup_api/auth/#keysign) using my Meetup id.

Fallback content is provided and should make sense in cases where a user has JS disabled.

Screenshot:
![homepage-next-event](https://cloud.githubusercontent.com/assets/38445/3417744/c60b1062-fe3c-11e3-94c9-200766128b73.png)