Now, only the empty squares contain a GestureDetector.
The GestureDetector is not necessary anymore in squares with pieces
because the tap is started when the drag is started.
This adds an option to dragging-and-dropping which is slightly hard on
smaller screens.
Fix promotions when tapping and fix handling of subsequently tapping two pieces of your color
Cancel tap if a drag is started (tapped square will not stay red in case a drag is started)
Change url strategy back to the hashtag thing
Change version
Fix bug that would not allow a piece move if you tried to take an opponents piece.
Fix the coloring of the last move after an invalid move was played.
Upgrading deps
