0.5.6

- [X] backlog
- [X] Update version
- [X] Use save-excursion - save-restriction - narrow-to-region instead of using region
- [X] Fix behavior orgtrello-buffer/end-of-line! When going to end of line in checkbox, we need to do it twice, fix.
- [X] Small refactoring about overlays
- [X] Release notes