Fix ViewPager.setCurrentItem() doesn't sync to tab

Fix ViewPager.setCurrentItem() doesn't sync to tab if page is not visible when called
Check if tabCount > 0 before attempting tabsContainer.getChildAt(position) when scrolling to child.

Ref : https://github.com/astuetz/PagerSlidingTabStrip/pull/89
if pager == null we don't need requestLayout()

astuetz#56
Fix tab reselection caused title become not selected

Fix tab reselection caused title become not selected and add onTabReselected() callback function
Minor typo fix
Proper fix for tab reselection caused title become not selected
Revert commit 8cc38b4 and proper fixes

Revert commit 8cc38b4 and proper fix for tab re-selection and separate the code in 2 lines to make it a bit more readable as jpardogo comment
Merge pull request #4 from xDragonZ/master

- Check if tabCount > 0 before attempting getChildAt 0
- if pager == null we don't need requestLayout()
- Fix click already selected tab  alpha
- Type fix