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