* add `keepTouchLocation` to let us choose whether touchLocation is back to -1 after label has been dragged.
* keep showing value if `keepTouchLocation` is true.
* Update README.md
* feat: when `keepTouchLocation` is true, bar is automatically deselect in a second after a gesture.
* fix: (BarChart) add animation when back to initial position after completing your gesture. and rename keepTouchLocation to animatedToBack.