update to new android-support-v4.jar
1. since android have new abstract class in android.database.DataSetObserver, we need to change the code to remove PagerAdapter.DataSetObserver interface relatived code
2. DirectionalViewPager.initViewPager will override ViewPager.initViewPager which will cause ViewPager var never initialed and get NullPointerException when ViewPager.draw() is called. So we changed the initViewPager to init() to avoid this override