Update PinnedSectionListView.java

fix bugs: 
in fast scroll mode, fs to top or bottom, the pinned shadow view get incollect section top;
in onScroll's some edge situation, we missed deal with the pinned shadow view.
Merge branch 'master' of git://github.com/hqwang/pinned-section-listview

Conflicts:
	library/src/com/hb/views/PinnedSectionListView.java
Code refactoring & bug fixes

- Pinned section detection algorithm was dramatically simplified.
- Fast scroll issues were fixed.
- Section click handler for a list with paddings was fixed.
- On layout is handled properly.
- Example application was extended with fast scroll and padding options.