Yogit

* Improve `yogit scrum report`: list contributions before completing the report
* Slack post now handles correctly channel mentions (member mentions is not working yet)

* Fix config file loading: do not raise an error when file does not exist

* Fix scrum report template migration of `yogit 1.12.0`. If you encountered the bug, remove `~/.yogit/scrum_report.yaml` to get the default one back

* Fix `yogit orga member ...` command: GitHub API became less permissive about param types

* Add `--label` filter to `yogit pr list` command
* Add Slack integration: thanks thomascarpentier for this contribution sponsored by Genymobile for hacktoberfest. It allows `yogit scrum report` to publish the report on Slack on your behalf. To configure it: `yogit account setup`

* Change `yogit review requested` output: print pull request title, don't print repository url anymore
* Add `--missed` option to `yogit review requested` command