Migrate from log4j to slf4j

src/main/java/com/r35157/nenjim/hubd/impl/ref/NenjimHubImpl.java

@@ -2,9 +2,9 @@ package com.r35157.nenjim.hubd.impl.ref;
 
 import com.r35157.nenjim.hubd.NenjimHub;
 import com.r35157.nenjim.hubd.journal.Journal;
-import org.apache.logging.log4j.LogManager;
-import org.apache.logging.log4j.Logger;
 import org.jetbrains.annotations.NotNull;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 public class NenjimHubImpl implements NenjimHub {
     @Override
@@ -17,6 +17,5 @@ public class NenjimHubImpl implements NenjimHub {
         log.warn("monitorJournal IS NOT IMPLEMENTED!");
     }
 
-
-    private static final Logger log = LogManager.getLogger(NenjimHubImpl.class);
+    private static final Logger log = LoggerFactory.getLogger(NenjimHubImpl.class);
 }