add sample for calendar customization

Thanks for releasing the new customization features.

As a result, I added a small sample to show how to customize the calendar.
I added customization for a basic calendar, not a ranged one. 
Feel free to ask for more customization if needed.

I also changed a bit the main layout of the sample activity to add the new button in the header bar. I just added a scroll view.

![screenshot_2014-06-10-14-55-14](https://cloud.githubusercontent.com/assets/3300620/3230117/3382166e-f09f-11e3-98af-422b515ee0ee.png)