Update Static Images for Landing/Sorter/Special Funds

CSS tweaks to accommodate images which scale with the page width (but maintain aspect ratio). To do that, the hero images must take up space, hence they cannot have absolute positioning. Also removed the unused/tested featured campaign code.

Before/afters:

Landing Header
![screen shot 2014-12-29 at 1 28 56 pm](https://cloud.githubusercontent.com/assets/326918/5572065/c1993a28-8f5e-11e4-8bfe-6d469de0df5d.png)
![screen shot 2014-12-29 at 1 28 03 pm](https://cloud.githubusercontent.com/assets/326918/5572074/d6b529d0-8f5e-11e4-9ef0-b963b524f38a.png)

Landing Funds Button
![screen shot 2014-12-29 at 1 29 04 pm](https://cloud.githubusercontent.com/assets/326918/5572088/0223b028-8f5f-11e4-9e92-ca51279f581f.png)
![screen shot 2014-12-29 at 1 28 14 pm](https://cloud.githubusercontent.com/assets/326918/5572113/3df68184-8f5f-11e4-8138-f45e5354624c.png)


Sorter Header
![screen shot 2014-12-29 at 1 29 14 pm](https://cloud.githubusercontent.com/assets/326918/5572119/4b423b80-8f5f-11e4-83e1-b3f072c3691c.png)
![screen shot 2014-12-29 at 1 28 24 pm](https://cloud.githubusercontent.com/assets/326918/5572123/51e05f26-8f5f-11e4-99a2-71120ffd9d50.png)


Special Funds Header
![screen shot 2014-12-29 at 1 29 27 pm](https://cloud.githubusercontent.com/assets/326918/5572130/6947bfb0-8f5f-11e4-894f-ee69793127dd.png)
![screen shot 2014-12-29 at 1 28 34 pm](https://cloud.githubusercontent.com/assets/326918/5572135/7553d280-8f5f-11e4-8d89-66abb401785e.png)