[issue-99] Add viewOnTop Mode (which is the google style pull-to-refresh)
[issue-100] Add new LoadingLayout( named mViewOnTopLoadingLayout ) for Google style pull-to-refresh
[issue-101] Add a loading layout container and an initialization method for google style pull-to-refresh
[issue-102] Add getActionBarSize(...) method
[issue-103] Call getActionBarSize(...) in initTopViewGroup() instead of using some magic number
[issue-104] Override onAttachedToWindow() for getting DecorView
[issue-105] Add updateUIForViewOnTopMode() for specially processing viewOnTop mode
insert a little bit of space for clear
[issue-106] Call updateUIForViewOnTopMode() in onAttachedToWindow()
[issue-107] Call updateUIForViewOnTopMode() in setMode()
[issue-108] Add mWindowAttached flag for checking that onAttachedToWindow() has been called.
[issue-109] Connect mViewOnTopLoadingLayout with PullToRefreshBase's events
[issue-110] Skip overscroll when mode is viewOnTop
[issue-111] Let OnSmoothScrollFinishedListener be called unconditionally in smoothScrollTo()
[issue-112] Add mTopViewLayout fading animation for prototype
Clean code, and remove some comment
Revert "Clean code and remove some comment"

This reverts commit 108ab633ef6701e9d41ba5ae4cfbf8c2435e947f.
[issue-113] Add mProgressBar and initialization for google style pull-to-refresh
[issue-114] Add mProgressBar animation and apply for prototype
[issue-115] Disable mListViewExtrasEnabled when mode is viewOnTop