Add software licenses (and About) activity

I tested it locally using `navigate().toAbout()` in ForecastActivity's onCreate(). Next PR will add a nav drawer.

![device-2014-09-10-102140](https://cloud.githubusercontent.com/assets/2678555/4214510/0ff9826e-38c4-11e4-9c0c-c925482bcb03.png)
![device-2014-09-10-102238](https://cloud.githubusercontent.com/assets/2678555/4214509/0ff423c8-38c4-11e4-89a4-6ac5506f854d.png)