Make TabPageIndicator move with ViewPager scrolling

Make TabPageIndicator move with ViewPager scrolling, the following screenshots show the effect:

![screenshot_2013-06-21-11-48-05](https://f.cloud.github.com/assets/1736705/685655/baa0b22e-da3c-11e2-837c-e14ac43b8f02.png)
![screenshot_2013-06-21-11-47-57](https://f.cloud.github.com/assets/1736705/685656/bf83f346-da3c-11e2-8371-061f984bf90c.png)
![screenshot_2013-06-21-11-47-49](https://f.cloud.github.com/assets/1736705/685657/c235856e-da3c-11e2-8ffa-0c8e9e56f8f8.png)