0.5.9

- [X] Backlog
- [X] Update version
- [X] Improve region card computation for sync card from trello.
- [X] Fix error on sync card from trello when nothing to sync.
- [X] Use defcustom instead of defvar for user customisation - CLOSE [[https://github.com/org-trello/org-trello/issues/196][#196]]
- [X] When not in card, explain why you cannot do the current action
- [X] Improve display of error when sync a card without title
- [X] Check package installation and fix what's needed
- [X] Release notes