SLF4J Logger rewrite part2 (#492) SLF4J stage 2 (final). - Added SLF4J Logger (fallback) and JDA internal Factory. - Added SLF4J to the README. - Replaced logs using variables with lazily built logs using SLF4J variable injection. - Combined multi-logs into a single log message (exceptions!) Also did: - Added try/catch in onTextMessage to print full JSON package when an error occurs outside of handling - Added handling for CHANNEL_UPDATE for a not existing category (commit: e9399b7)