0.3.3

- [X] Issue when installing on melpa reported wrongly on melpa and reported back https://github.com/ardumont/org-trello/issues/117
- [X] Fix typo when-let in -when-let
- [X] Remove org as a dependency, the plugins org- do not seem to declare it + problem in dependency
- [X] Upgrade to dash 2.5.0
- [X] Clarify the possible manipulation to install the package as a file or directly from the multiple repository
- [X] Integration test to install the file with marmalade
- [X] Integration test to install the file with melpa
- [X] Integration test to fully install the package on marmalade
- [X] Integration test to fully install the package on melpa
- [X] Update README-dev.md about those targets
- [X] Decline these tests with multiple emacs versions
- [X] Use these targets on travis (even if the feedback will be way longer, it's better than no feedback)
- [X] Upgrade version
- [X] Ensure org-trello works with emacs 24.4 (how do i install it...)