Duck update previews

* Update screenshots.

![preview1](https://f.cloud.github.com/assets/40106/1405880/6b92e9d6-3d42-11e3-9750-d83e06f607ea.png)
![preview7](https://f.cloud.github.com/assets/40106/1405881/6bc563fc-3d42-11e3-8dc5-7e2fe8599a75.png)
![preview6](https://f.cloud.github.com/assets/40106/1405882/6be34188-3d42-11e3-8793-a2607970b73f.png)
![preview5](https://f.cloud.github.com/assets/40106/1405883/6be9e9c0-3d42-11e3-93e2-5861ff8188dd.png)
![preview3](https://f.cloud.github.com/assets/40106/1405886/6beac264-3d42-11e3-8498-d15930bf5f23.png)
![preview4](https://f.cloud.github.com/assets/40106/1405884/6bea1f58-3d42-11e3-9696-813540fca2e3.png)
![preview2](https://f.cloud.github.com/assets/40106/1405885/6beabe22-3d42-11e3-9db7-f695eefe29b7.png)

* Update README.
* Fixed README title.