v0.8.1

Fixed

• Unregistering was not working correctly when the same callback was added for
  multiple events. (#75)
• The plot.marker.label.color setting now works in a way that modifies the
  previously calculated color based on the transparency channel of the color
  setting. (#144)
• When rapidly clicking multiple times while the selection animation has not
  finished, the library is aborted due to an exception.
• At times, the chosen marker would disappear from the selections during
  rapid mouse actions, leading to an exception being triggered.
• Sometimes, during mouse actions, when the tooltip animation disappeared, the
  marker information was null. With a new mouse action, when other tooltip
  appeared, the marker transformation went from null to null, which caused an
  exception.