Add some tests

Remove redundant code

Fix ring stuff

Add objstore cleanup on diff processed

Make persister callback to run in goroutine

Fix logging

Refactoring

Update config parsing, add possibility to bind env variables

Made persister to skip already processed diffs

Fix pg reconnect

Refactoring

Update plugin interface, update importer

Merge pull request #13 from ValerySidorin/dev

Resolve linter issues

Merge pull request #12 from ValerySidorin/dev