Group feature now works with Vault with any perms plugin that Vault supports.
Added command /jail info <player>; it prints in chat a bunch of the info stored in the player data file.
/jail info <player> also comes with two new messages: infoFailedPlayerNeverJoined and infoFailedPlayerNotJailed.
Now it alerts in console when loaded config.yml differs with plugin's config.yml.
Cache offline player list on load time, will probably perform better on servers that had tons of players.