Homepage stats bar

It works! I wasn't sure how we want to calculate the total lbs of CO2 avoided and number of citizens impacted, so those are left hardcoded for now. Also, I had to make it invisible on mobile because it gets too small :(

![screen shot 2014-12-20 at 5 25 05 pm](https://cloud.githubusercontent.com/assets/1168853/5516884/6b40eb3c-886d-11e4-8a92-e199498f17e9.png)

I also added in a library called svg4everybody which will allow the stuff I'm doing with the svg images to work with older browsers.