Rewrite a big part of the application

* Fix issue with new github api (issue + pr)
* Added symfony/var-dumper
* Rename Issue to Object
* Rename IssueUtility to ObjectUtility
* Remove the cache layer inside the Object entity, now we force the datetime of createAt, closedAt
* bump to 0.3.0
* Use the new Github Paginator (vendored in knplabs/github-api)