v1.3.0

Added

• Open the current note in an external editor with E or Ctrl-e, using
  $VISUAL, $EDITOR, or vi, saving local edits before launch and reloading
  the note after the editor exits (#2).
• Undo and redo edits in the note editor with Ctrl-z and Ctrl-Shift-Z
  (or Ctrl-y). Typed words and consecutive deletions are undone together,
  and the history is cleared when another note is loaded or the note is
  reloaded from disk.