Redesign AboutDialog

![ttyh-about-dialog](https://cloud.githubusercontent.com/assets/4698994/5563937/829694d8-8eaf-11e4-8986-123b42005ac2.png)
![ttyh-license-dialog](https://cloud.githubusercontent.com/assets/4698994/5563938/9429af46-8eaf-11e4-9b5f-8f9c3fa8d57b.png)