0.2.9

- [X] Remove org-trello.el at the root of the code (as the package generates this file and the test load without it, no longer needs to be gitted)
- [X] Invisible checkbox identifier - https://github.com/ardumont/org-trello/issues/98
- [X] Fix sync from trello which loses the state of the checkboxes
- [X] Fix tests break since org-trello.el has been destroyed and simplify the testing
- [X] Overload the C-e mapping to go at the end of the line for the org-trello mode
- [X] Update doc
- [X] Release notes