Can not open https://jitpack.io/com/github/nukc/LoadMoreWrapper/v1.9.2 , so release v1.9.3

Migrate to AndroidX

add function: setNotShowFooterWhenNotCoveredScreen #25

update canScroll(), fix canScrollVertically(-1) is always false

refactor: sync hasStableIds

feat: func setHasStableIds and setOnStableIdCallback

update gradle
compileSdkVersion: 28
buildToolsVersion '28.0.3'
targetSdkVersion 28
supportLibVersion = '28.0.0'

support show load failed view and can retry click to load more

make NoMoreHolder and FooterHolder public

add getFooterView() and getNoMoreView()