v0.2.0

Added

• add_child_at_mpl_point() function to simplify needing to separately call three
  different functions to add a child, get pixel converted mpl data locs, and
  then connect the new child
• display_output() function to support creating an ipywidgets Output and
  rendering any displayable such as a static matplotlib figure with a single call

Fixed

• Missing top level module imports
• Connection to matplotlib ipympl canvas not always using the instance within the
  container