Release v2.2.0

[PabloKowalczyk]

PRs

• [Add task:debug command #287] Add task:debug command
• [Improve TravisCI configuration #288] Improve TravisCI configuration
• [Remove "dev_tools" service from docker-compose #290] Remove "dev_tools" service from docker-compose
• [Remove box from vendor bin #291] Remove box from vendor bin
• [Drop Symfony 4.2 support #292] Drop Symfony 4.2 support
• [Update docs for Symfony 5 locking #294] Update docs for Symfony 5 locking, thanks to @hashnz
• [Add option to ignore empty context in monolog #233] Add option to ignore empty context in monolog
• [Add ConfigurationInterface #297] Add ConfigurationInterface
• [Migrate to "opis\closure" #299] Migrate to opis\closure
• [Update dev tools #300] Update dev tools
• [Implement logger factory rfc #298] Implement logger factory rfc
• [Add "status" column to roadmap #304] Add "status" column to roadmap
• [Test Symfony 5.1 compatibility #305] Test Symfony 5.1 compatibility