Brazil world cup

Adds a bunch of hero images and a new banner for the upcoming world cup.

![brazil](https://cloud.githubusercontent.com/assets/708296/3093846/458e74e0-e5b6-11e3-9bcc-c6425a049350.png)
![belo-horizonte](https://cloud.githubusercontent.com/assets/708296/3093849/45d91a2c-e5b6-11e3-9d64-2ac255dcf4a8.png)
![brasilia](https://cloud.githubusercontent.com/assets/708296/3093847/45a57082-e5b6-11e3-90e6-93c46f1575f6.png)
![cuiaba](https://cloud.githubusercontent.com/assets/708296/3093848/45aa0b88-e5b6-11e3-9c59-0d084b60f16d.png)
![curitiba](https://cloud.githubusercontent.com/assets/708296/3093850/45f66bc2-e5b6-11e3-8ce3-3df9bb7f215d.png)
![fortaleza](https://cloud.githubusercontent.com/assets/708296/3093845/457943ae-e5b6-11e3-8dda-825f86126091.png)
![manaus](https://cloud.githubusercontent.com/assets/708296/3093851/460653b6-e5b6-11e3-978a-0bb5d84378d2.png)
![natal](https://cloud.githubusercontent.com/assets/708296/3093852/460e0dc2-e5b6-11e3-853e-8df5ec1b4c76.png)
![porto-alegre](https://cloud.githubusercontent.com/assets/708296/3093855/462738b0-e5b6-11e3-95e8-207534d7b1e5.png)
![recife](https://cloud.githubusercontent.com/assets/708296/3093854/461f885e-e5b6-11e3-8a01-9bae8cbf31a2.png)
![salvador](https://cloud.githubusercontent.com/assets/708296/3093853/4619ccfc-e5b6-11e3-8eef-44ea5970d102.png)
![sao-paulo](https://cloud.githubusercontent.com/assets/708296/3093856/465b61a8-e5b6-11e3-83a0-04e5828e2b0a.png)