fix leaf node icon and make custom icon easily

add `onDragEnd` API and fix related issues.

change & add class, maybe fix ant-design/ant-design#3105

fix dragNodeHighlight

add halfCheckedKeys, ref react-component#25

fix react-component#24

mr, bump version

merge react-component#18, bump version

fixed react-component#12

merge react-component#14 and release new version