Change Atarashii icon (& Beta icon).

This commit will change the Atarashii icon (ref #179).

![naamloos](https://cloud.githubusercontent.com/assets/5322473/3737263/4f9b6c6c-1735-11e4-952d-c9b98b320032.png)
![naamloos2](https://cloud.githubusercontent.com/assets/5322473/3737339/13dacf0a-1736-11e4-94a5-6292f884d7d0.png)